arm64: random: Remove no longer needed prototypes

Commit 9bceb80b ("arm64: kaslr: Use standard early random
function") removed the direct calls of the __arm64_rndr() and
__early_cpu_has_rndr() functions, but left the dummy prototypes in the
 #else branch of the #ifdef CONFIG_ARCH_RANDOM guard.

Remove the redundant prototypes, as they have no users outside of
this header file.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20201006194453.36519-1-andre.przywara@arm.com


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