soc: arc: snps_arc_iot: move SYSCLK_DEFAULT_IOSC_HZ to sysconf

sysconf source file is the only user of such definition, so move it
there.

Signed-off-by: Gerard Marull-Paretas <gerard.marull@nordicsemi.no>

soc/arc/snps_arc_iot/soc.h

@@ -16,9 +16,6 @@
 
 #include <zephyr/sys/util.h>
 
-/* default system clock */
-#define SYSCLK_DEFAULT_IOSC_HZ			MHZ(16)
-
 /* ARC EM Core IRQs */
 #include "soc_irq.h"
 

soc/arc/snps_arc_iot/sysconf.c

@@ -7,6 +7,8 @@
 #include "soc.h"
 #include "sysconf.h"
 
+/* default system clock */
+#define SYSCLK_DEFAULT_IOSC_HZ			MHZ(16)
 
 #define PLL_CLK_IN	(SYSCLK_DEFAULT_IOSC_HZ / 1000000)  /* PLL clock in */