[ACPI] handle const char * __FUNCTION__ in debug code

build warning: discards qualifiers from pointer target type
when mixing "const char *" and "char *"

We should probably update the routines to expect const,
but easier for now to shut up the warning with 1 cast.
Signed-off-by: Len Brown <len.brown@intel.com>

include/acpi/platform/acgcc.h

@@ -46,7 +46,7 @@
 
 /* Function name is used for debug output. Non-ANSI, compiler-dependent */
 
-#define ACPI_GET_FUNCTION_NAME          __FUNCTION__
+#define ACPI_GET_FUNCTION_NAME          (char *) __FUNCTION__
 
 /* This macro is used to tag functions as "printf-like" because
  * some compilers (like GCC) can catch printf format string problems.