arm64/signal: Remove redundant size validation from parse_user_sigframe()

arm64/signal: Remove redundant size validation from parse_user_sigframe()

There is some minimal size validation in parse_user_sigframe() however
all of the individual parsing functions perform frame specific validation
of the sizing information, remove the frame specific size checks in the
core so that there isn't any confusion about what we validate for size.

Since the checks in the SVE and ZA parsing are after we have read the
relevant context and since they won't report an error if the frame is
undersized they are adjusted to check for this before doing anything else.

Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20221212-arm64-signal-cleanup-v3-2-4545c94b20ff@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>