arm64/cpufeature: Fix field sign for DIT hwcap detection

arm64/cpufeature: Fix field sign for DIT hwcap detection

Since it was added our hwcap for DIT has specified that DIT is a signed
field but this appears to be incorrect, the two values for the enumeration
are:

	0b0000	NI
	0b0001	IMP

which look like a normal unsigned enumeration and the in-kernel DIT usage
added by 01ab991fc0ee ("arm64: Enable data independent timing (DIT) in the
kernel") detects the feature with an unsigned enum. Fix the hwcap to specify
the field as unsigned.

Fixes: 7206dc93a58f ("arm64: Expose Arm v8.4 features")
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20221207-arm64-sysreg-helpers-v3-1-0d71a7b174a8@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>