arm64: vdso: Convert to modern assembler annotations

In an effort to clarify and simplify the annotation of assembly
functions new macros have been introduced. These replace ENTRY and
ENDPROC with two different annotations for normal functions and those
with unusual calling conventions. Convert the assembly function in the
arm64 VDSO to the new macros.

Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>