selftests: riscv: fix v_exec_initval_nolibc.c

Vector registers are zero initialized by the kernel. Stop accepting
"all ones" as a clean value.

Note that this was not working as expected given that
	value == 0xff
can be assumed to be always false by the compiler as value's range is
[-128, 127]. Both GCC (-Wtype-limits) and clang
(-Wtautological-constant-out-of-range-compare) warn about this.

Reviewed-by: Charlie Jenkins <charlie@rivosinc.com>
Tested-by: Charlie Jenkins <charlie@rivosinc.com>
Signed-off-by: Ignacio Encinas <ignacio@iencinas.com>
Link: https://lore.kernel.org/r/20250306-fix-v_exec_initval_nolibc-v2-1-97f9dc8a7faf@iencinas.com
Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>

Author: IEncinas10

tools/testing/selftests/riscv/vector/v_exec_initval_nolibc.c

@@ -6,17 +6,16 @@
  * the values. To further ensure consistency, this file is compiled without
  * libc and without auto-vectorization.
  *
- * To be "clean" all values must be either all ones or all zeroes.
+ * To be "clean" all values must be all zeroes.
  */
 
 #define __stringify_1(x...)	#x
 #define __stringify(x...)	__stringify_1(x)
 
 int main(int argc, char **argv)
 {
-	char prev_value = 0, value;
+	char value = 0;
 	unsigned long vl;
-	int first = 1;
 
 	if (argc > 2 && strcmp(argv[2], "x"))
 		asm volatile (
@@ -44,14 +43,11 @@ int main(int argc, char **argv)
 			"vsrl.vi " __stringify(register) ", " __stringify(register) ", 8\n\t" \
 			".option pop\n\t"					\
 			: "=r" (value));					\
-		if (first) {							\
-			first = 0;						\
-		} else if (value != prev_value || !(value == 0x00 || value == 0xff)) { \
+		if (value != 0x00) {						\
 			printf("Register " __stringify(register)		\
 				" values not clean! value: %u\n", value);	\
 			exit(-1);						\
 		}								\
-		prev_value = value;						\
 	}									\
 })