FROMLIST: [PATCH] arm64: compat: Expose offset to registers in sigframes

FROMLIST: [PATCH] arm64: compat: Expose offset to registers in sigframes

(cherry picked from url https://patchwork.kernel.org/patch/10006025/)

This will be needed to provide unwinding information in compat
sigreturn trampolines, part of the future compat vDSO. There is no
obvious header the compat_sig* struct's should be moved to, so let's
put them in signal32.h.

Also fix minor style issues reported by checkpatch.

Signed-off-by: Kevin Brodsky <kevin.brodsky@arm.com>
Signed-off-by: Mark Salyzyn <salyzyn@android.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Andy Gross <andy.gross@linaro.org>
Cc: Dave Martin <Dave.Martin@arm.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Bug: 63737556
Bug: 20045882
Change-Id: I9c23dd6b56ca48c0953cbf78ccb7b49ded906052