arm64: vdso32: Code clean up

The compat vdso library had some checks that are not anymore relevant.

Remove the unused code from the compat vDSO library.

Note: This patch is preparatory for a future one that will introduce
asm/vdso/processor.h on arm64.

Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/lkml/20200317122220.30393-19-vincenzo.frascino@arm.com
Link: https://lkml.kernel.org/r/20200320145351.32292-19-vincenzo.frascino@arm.com