ARM: debug: fix DEBUG_UNCOMPRESS help for !MULTIPLATFORM

Commit 84fc863 ("ARM: make ARCH_MULTIPLATFORM user-visible") modified
DEBUG_UNCOMPRESS to prevent using it with multiplatform kernels.

Update the help text, remove references to multiplatform.

Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

arch/arm/Kconfig.debug

@@ -1809,15 +1809,8 @@ config DEBUG_UNCOMPRESS
 		     (!DEBUG_TEGRA_UART || !ZBOOT_ROM) && \
 		     !DEBUG_BRCMSTB_UART && !DEBUG_SEMIHOSTING
 	help
-	  This option influences the normal decompressor output for
-	  multiplatform kernels.  Normally, multiplatform kernels disable
-	  decompressor output because it is not possible to know where to
-	  send the decompressor output.
-
-	  When this option is set, the selected DEBUG_LL output method
-	  will be re-used for normal decompressor output on multiplatform
-	  kernels.
-
+	  Say Y here to enable debug output in the decompressor code, using
+	  the selected DEBUG_LL output method.
 
 config UNCOMPRESS_INCLUDE
 	string