arm64: alternative: simplify passing alt_region

arm64: alternative: simplify passing alt_region

In __apply_alternatives() we take a pointer to void which we later
assign to a pointer to struct alt_region. As all callers are passing a
pointer to struct alt_region to begin with, it's simpler and more robust
to take a pointer to struct alt region, so let's do so and avoid the
need for a temporary variable.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will@kernel.org>
Acked-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20210416163032.10857-1-mark.rutland@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>