Fix the following clang error in sve_vl():

In file included from arm/selftest.c:16:
kvm-unit-tests/lib/asm/processor.h:163:16:
error: value size does not match register size specified by the
constraint and modifier [-Werror,-Wasm-operand-widths]
                     : "=r" (vl));
                             ^
kvm-unit-tests/lib/asm/processor.h:162:14:
note: use constraint modifier "w"
                     "rdvl %0, #8"
                           ^~
                           %w0
1 error generated.

Fixes: d47d370c8f ("arm: Add test for FPU/SIMD context save/restore")
Signed-off-by: Raghavendra Rao Ananta <rananta@google.com>
---
 lib/arm64/asm/processor.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/arm64/asm/processor.h b/lib/arm64/asm/processor.h
index b28d41fd..e261e74d 100644
--- a/lib/arm64/asm/processor.h
+++ b/lib/arm64/asm/processor.h
@@ -159,7 +159,7 @@ static inline int sve_vl(void)
 	int vl;
 
 	asm volatile(".arch_extension sve\n"
-		     "rdvl %0, #8"
+		     "rdvl %w0, #8"
 		     : "=r" (vl));
 
 	return vl;
-- 
2.47.0.105.g07ac214952-goog