selftests/bpf: Verify zero-extension behavior in load-acquire tests

Verify that 8-, 16- and 32-bit load-acquires are zero-extending by using
immediate values with their highest bit set. Do the same for the 64-bit
variant to keep the style consistent.

Acked-by: Björn Töpel <[e-mail]>
Reviewed-by: Pu Lehui <[e-mail]>
Tested-by: Björn Töpel <[e-mail]> # QEMU/RVA23
Signed-off-by: Peilin Ye <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Alexei Starovoitov <[e-mail]>

tools/testing/selftests/bpf/progs/verifier_load_acquire.c

···
 {
 	asm volatile (
 	"r0 = 0;"
-	"w1 = 0x12;"
+	"w1 = 0xfe;"
 	"*(u8 *)(r10 - 1) = w1;"
 	".8byte %[load_acquire_insn];" // w2 = load_acquire((u8 *)(r10 - 1));
 	"if r2 == r1 goto 1f;"
···
 {
 	asm volatile (
 	"r0 = 0;"
-	"w1 = 0x1234;"
+	"w1 = 0xfedc;"
 	"*(u16 *)(r10 - 2) = w1;"
 	".8byte %[load_acquire_insn];" // w2 = load_acquire((u16 *)(r10 - 2));
 	"if r2 == r1 goto 1f;"
···
 {
 	asm volatile (
 	"r0 = 0;"
-	"w1 = 0x12345678;"
+	"w1 = 0xfedcba09;"
 	"*(u32 *)(r10 - 4) = w1;"
 	".8byte %[load_acquire_insn];" // w2 = load_acquire((u32 *)(r10 - 4));
 	"if r2 == r1 goto 1f;"
···
 {
 	asm volatile (
 	"r0 = 0;"
-	"r1 = 0x1234567890abcdef ll;"
+	"r1 = 0xfedcba0987654321 ll;"
 	"*(u64 *)(r10 - 8) = r1;"
 	".8byte %[load_acquire_insn];" // r2 = load_acquire((u64 *)(r10 - 8));
 	"if r2 == r1 goto 1f;"