arm64/sysreg: Enforce whole word match for open/close tokens

Opening and closing tokens can also match on words with common prefixes
like "Endsysreg" vs "EndsysregFields". This could potentially make the
script go wrong in weird ways so make it fall through to the fatal
unhandled statement catcher if it doesn't fully match the current
block.

Closing ones also get expect_fields(1) to ensure nothing other than
whitespace follows.

Signed-off-by: James Clark <james.clark@linaro.org>
Acked-by: Will Deacon <will@kernel.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/20250115162600.2153226-3-james.clark@linaro.org


Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>