arm64: mark __system_matches_cap as __maybe_unused

mainline inclusion
from mainline-v5.11-rc1
commit 701f4906
category: performance
bugzilla: https://e.gitee.com/open_euler/issues/list?issue=I4SCW7
CVE: NA

-------------------------------------------------------------------------

Now that the PAN toggling has been removed, the only user of
__system_matches_cap() is has_generic_auth(), which is only built when
CONFIG_ARM64_PTR_AUTH is selected, and Qian reports that this results in
a build-time warning when CONFIG_ARM64_PTR_AUTH is not selected:

| arch/arm64/kernel/cpufeature.c:2649:13: warning: '__system_matches_cap' defined but not used [-Wunused-function]
|  static bool __system_matches_cap(unsigned int n)
|              ^~~~~~~~~~~~~~~~~~~~

It's tricky to restructure things to prevent this, so let's mark
__system_matches_cap() as __maybe_unused, as we used to do for the other
user of __system_matches_cap() which we just removed.
Reported-by: NQian Cai <qcai@redhat.com>
Suggested-by: NQian Cai <qcai@redhat.com>
Signed-off-by: NMark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/20201203152403.26100-1-mark.rutland@arm.comSigned-off-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NZhen Lei <thunder.leizhen@huawei.com>
Reviewed-by: NHanjun Guo <guohanjun@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

arch/arm64/kernel/cpufeature.c

@@ -2750,7 +2750,7 @@ bool this_cpu_has_cap(unsigned int n)
  * - The SYSTEM_FEATURE cpu_hwcaps may not have been set.
  * In all other cases cpus_have_{const_}cap() should be used.
  */
-static bool __system_matches_cap(unsigned int n)
+static bool __maybe_unused __system_matches_cap(unsigned int n)
 {
 	if (n < ARM64_NCAPS) {
 		const struct arm64_cpu_capabilities *cap = cpu_hwcaps_ptrs[n];