WIP: selftests/bpf: Fix arm perf ctx for verifier_global_subprogs

Use bpf_user_pt_regs_t for perf ctx arg to avoid below failures. This type
previously added because "long" type in struct pt_regs on 32-bit arm evals
to wrong size in 64-bit BPF VM, resulting in errors like:

run_subtest:PASS:obj_open_mem 0 nsec
libbpf: prog 'arg_tag_ctx_perf': BPF program load failed: -EINVAL
libbpf: prog 'arg_tag_ctx_perf': failed to load: -EINVAL
libbpf: failed to load object 'verifier_global_subprogs'
run_subtest:FAIL:unexpected_load_failure unexpected error: -22 (errno 22)
VERIFIER LOG:
=============
func#0 @0
func#1 @15
func#2 @21
func#3 @23
func#4 @25
Live regs before insn:
      0: .12345.... (bf) r6 = r1
      1: .123456... (85) call pc+13
      2: 0.23456... (bc) w7 = w0
      3: ..234567.. (bf) r1 = r6
      4: .1234567.. (85) call pc+16
      5: 0.234567.. (bc) w8 = w0
      6: ..2345678. (0c) w8 += w7
      7: ..23456.8. (bf) r1 = r6
      8: .123456.8. (85) call pc+14
      9: 0.23456.8. (0c) w8 += w0
     10: ..23456.8. (bf) r1 = r6
     11: .12345..8. (85) call pc+13
     12: 0.......8. (0c) w8 += w0
     13: ........8. (bc) w0 = w8
     14: 0......... (95) exit
     15: .1........ (18) r2 = 0xdfc7d008
     17: .12....... (b4) w3 = 1024
     18: .123...... (b7) r4 = 0
     19: .1234..... (85) call bpf_get_stack#67
     20: 0......... (95) exit
     21: .......... (b4) w0 = 0
     22: 0......... (95) exit
     23: .......... (b4) w0 = 0
     24: 0......... (95) exit
     25: .......... (b4) w0 = 0
     26: 0......... (95) exit
arg#0 reference type('UNKNOWN ') size cannot be determined: -22
0: R1=ctx() R10=fp0
; int arg_tag_ctx_perf(void *ctx) @ verifier_global_subprogs.c:271
0: (bf) r6 = r1                       ; R1=ctx() R6=ctx()
; return subprog_ctx_tag(ctx) + @ verifier_global_subprogs.c:273
1: (85) call pc+13
Func#1 ('subprog_ctx_tag') is global and assumed valid.
2: R0=scalar()
2: (bc) w7 = w0                       ; R0=scalar() R7=scalar(smin=0,smax=umax=0xffffffff,var_off=(0x0; 0xffffffff))
; perf_subprog_regs(ctx) + @ verifier_global_subprogs.c:274
3: (bf) r1 = r6                       ; R1=ctx() R6=ctx()
4: (85) call pc+16
arg#0 should be `struct bpf_perf_event_data *`
Caller passes invalid args into func#2 ('perf_subprog_regs')
processed 5 insns (limit 1000000) max_states_per_insn 0 total_states 0 peak_states 0 mark_read 0
=============
torvalds#514/14  verifier_global_subprogs/arg_tag_ctx_perf:FAIL

Signed-off-by: Tony Ambardar <tony.ambardar@gmail.com>

Author: guidosarducci

tools/testing/selftests/bpf/progs/verifier_global_subprogs.c

@@ -248,6 +248,8 @@ __weak int perf_subprog_regs(
 	void *ctx __arg_ctx
 #elif defined(bpf_target_loongarch) || defined(bpf_target_arm64) || defined(bpf_target_powerpc)
 	struct user_pt_regs *ctx __arg_ctx
+#elif defined(bpf_target_arm)
+	bpf_user_pt_regs_t *ctx __arg_ctx
 #else
 	struct pt_regs *ctx __arg_ctx
 #endif