arm64: Include the clkdev.h generic header

This patch updates the arm64 asm/Kbuild file to include the clkdev.h
generic header.
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Viresh Kumar <Viresh.kumar@linaro.org>

arch/arm64/include/asm/Kbuild

@@ -3,6 +3,7 @@
 generic-y += bug.h
 generic-y += bugs.h
 generic-y += checksum.h
+generic-y += clkdev.h
 generic-y += cputime.h
 generic-y += current.h
 generic-y += delay.h