signal/arm64: Only perform one esr_to_fault_info call in do_page_fault

As this work is truly common between all of the signal sending cases
there is no need to repeat it between the different cases.

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Tested-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>