refactor(amu): use new AMU feature check routines

The AMU extension code was using its own feature detection routines.
Replace them with the generic CPU feature handlers (defined in
arch_features.h), which get updated to cover the v1p1 variant as well.

Change-Id: I8540f1e745d7b02a25a6c6cdf2a39d6f5e21f2aa
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
diff --git a/include/arch/aarch64/arch_features.h b/include/arch/aarch64/arch_features.h
index f827895..d7116a7 100644
--- a/include/arch/aarch64/arch_features.h
+++ b/include/arch/aarch64/arch_features.h
@@ -255,8 +255,16 @@
 	return read_feat_amu_id_field() >= ID_AA64PFR0_AMU_V1;
 }
 
-static inline bool is_armv8_6_feat_amuv1p1_present(void)
+static inline bool is_feat_amuv1p1_supported(void)
 {
+	if (ENABLE_FEAT_AMUv1p1 == FEAT_STATE_DISABLED) {
+		return false;
+	}
+
+	if (ENABLE_FEAT_AMUv1p1 == FEAT_STATE_ALWAYS) {
+		return true;
+	}
+
 	return read_feat_amu_id_field() >= ID_AA64PFR0_AMU_V1P1;
 }