arm64: cpufeature: Don't enforce system-wide SPE capability

The statistical profiling extension (SPE) is an optional feature of
ARMv8.1 and is unlikely to be supported by all of the CPUs in a
heterogeneous system.

This patch updates the cpufeature checks so that such systems are not
tainted as unsupported.
Acked-by: NMark Rutland <mark.rutland@arm.com>
Reviewed-by: NSuzuki Poulose <suzuki.poulose@arm.com>
Signed-off-by: NWill Deacon <will.deacon@arm.com>

arch/arm64/include/asm/sysreg.h

@@ -190,6 +190,7 @@
 #define ID_AA64MMFR2_CNP_SHIFT		0
 
 /* id_aa64dfr0 */
+#define ID_AA64DFR0_PMSVER_SHIFT	32
 #define ID_AA64DFR0_CTX_CMPS_SHIFT	28
 #define ID_AA64DFR0_WRPS_SHIFT		20
 #define ID_AA64DFR0_BRPS_SHIFT		12

arch/arm64/kernel/cpufeature.c

@@ -180,7 +180,8 @@ static const struct arm64_ftr_bits ftr_id_mmfr0[] = {
 };
 
 static const struct arm64_ftr_bits ftr_id_aa64dfr0[] = {
-	ARM64_FTR_BITS(FTR_STRICT, FTR_EXACT, 32, 32, 0),
+	ARM64_FTR_BITS(FTR_STRICT, FTR_EXACT, 36, 28, 0),
+	ARM64_FTR_BITS(FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64DFR0_PMSVER_SHIFT, 4, 0),
 	ARM64_FTR_BITS(FTR_STRICT, FTR_LOWER_SAFE, ID_AA64DFR0_CTX_CMPS_SHIFT, 4, 0),
 	ARM64_FTR_BITS(FTR_STRICT, FTR_LOWER_SAFE, ID_AA64DFR0_WRPS_SHIFT, 4, 0),
 	ARM64_FTR_BITS(FTR_STRICT, FTR_LOWER_SAFE, ID_AA64DFR0_BRPS_SHIFT, 4, 0),