selftest/arm64: Fix sve2p1_sigill() to hwcap test

The FEAT_SVE2p1 is indicated by ID_AA64ZFR0_EL1.SVEver. However,
the BFADD requires the FEAT_SVE_B16B16, which is indicated by
ID_AA64ZFR0_EL1.B16B16. This could cause the test to incorrectly
fail on a CPU that supports FEAT_SVE2.1 but not FEAT_SVE_B16B16.

LD1Q Gather load quadwords which is decoded from SVE encodings and
implied by FEAT_SVE2p1.

Fixes: c5195b0 ("kselftest/arm64: Add SVE 2.1 to hwcap test")
Signed-off-by: Yifan Wu <wuyifan50@huawei.com>
Reviewed-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Will Deacon <will@kernel.org>

Author: Yifan Wu

tools/testing/selftests/arm64/abi/hwcap.c

@@ -475,8 +475,8 @@ static void sve2_sigill(void)
 
 static void sve2p1_sigill(void)
 {
-	/* BFADD Z0.H, Z0.H, Z0.H */
-	asm volatile(".inst 0x65000000" : : : "z0");
+	/* LD1Q {Z0.Q}, P0/Z, [Z0.D, X0] */
+	asm volatile(".inst 0xC400A000" : : : "z0");
 }
 
 static void sve2p2_sigill(void)