arm64: armv8_deprecated: fix unused-function error

If CONFIG_SWP_EMULATION is not set and
CONFIG_CP15_BARRIER_EMULATION is not set,
aarch64-linux-gnu complained about unused-function :

arch/arm64/kernel/armv8_deprecated.c:67:21: error: ‘aarch32_check_condition’ defined but not used [-Werror=unused-function]
 static unsigned int aarch32_check_condition(u32 opcode, u32 psr)
                     ^~~~~~~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors

To fix this warning, modify aarch32_check_condition() with __maybe_unused.

Fixes: 0c5f4162 ("arm64: armv8_deprecated: move aarch32 helper earlier")
Signed-off-by: Ren Zhijie <renzhijie2@huawei.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/20221124022429.19024-1-renzhijie2@huawei.comSigned-off-by: Will Deacon <will@kernel.org>

arch/arm64/kernel/armv8_deprecated.c

@@ -64,7 +64,7 @@ struct insn_emulation {
 
 #define	ARM_OPCODE_CONDITION_UNCOND	0xf
 
-static unsigned int aarch32_check_condition(u32 opcode, u32 psr)
+static unsigned int __maybe_unused aarch32_check_condition(u32 opcode, u32 psr)
 {
 	u32 cc_bits  = opcode >> 28;