arm64: perf: Mark all accessor functions inline

When just including <asm/arm_pmuv3.h>:

    arch/arm64/include/asm/arm_pmuv3.h:31:13: error: ‘write_pmevtypern’ defined but not used [-Werror=unused-function]
       31 | static void write_pmevtypern(int n, unsigned long val)
	  |             ^~~~~~~~~~~~~~~~
    arch/arm64/include/asm/arm_pmuv3.h:24:13: error: ‘write_pmevcntrn’ defined but not used [-Werror=unused-function]
       24 | static void write_pmevcntrn(int n, unsigned long val)
	  |             ^~~~~~~~~~~~~~~
    arch/arm64/include/asm/arm_pmuv3.h:16:22: error: ‘read_pmevcntrn’ defined but not used [-Werror=unused-function]
       16 | static unsigned long read_pmevcntrn(int n)
	  |                      ^~~~~~~~~~~~~~

Fix this by adding the missing "inline" keywords to the three accessor
functions that lack them.

Fixes: df29ddf4 ("arm64: perf: Abstract system register accesses away")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Marc Zyngier <maz@kernel.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/d53a19043c0c3bd25f6c203e73a2fb08a9661824.1683561482.git.geert+renesas@glider.be


Signed-off-by: Will Deacon <will@kernel.org>