selftests/powerpc: Fix uninitialized variable warning

Patch fixes uninitialized variable warning in bad_accesses test
which causes the selftests build to fail in older distibutions

bad_accesses.c: In function ‘bad_access’:
bad_accesses.c:52:9: error: ‘x’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
   printf("Bad - no SEGV! (%c)\n", x);
         ^
cc1: all warnings being treated as errors
Signed-off-by: Harish <harish@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201201092403.238182-1-harish@linux.ibm.com

tools/testing/selftests/powerpc/mm/bad_accesses.c

@@ -38,7 +38,7 @@ static void segv_handler(int n, siginfo_t *info, void *ctxt_v)
 
 int bad_access(char *p, bool write)
 {
-	char x;
+	char x = 0;
 
 	fault_code = 0;
 	fault_addr = 0;