arm64/cache: Fix cache_type_cwg() for register generation

arm64/cache: Fix cache_type_cwg() for register generation

Ard noticed that since we converted CTR_EL0 to automatic generation we have
been seeing errors on some systems handling the value of cache_type_cwg()
such as

   CPU features: No Cache Writeback Granule information, assuming 128

This is because the manual definition of CTR_EL0_CWG_MASK was done without
a shift while our convention is to define the mask after shifting. This
means that the user in cache_type_cwg() was broken as it was written for
the manually written shift then mask. Fix this by converting to use
SYS_FIELD_GET().

The only other field where the _MASK for this register is used is IminLine
which is at offset 0 so unaffected.

Fixes: 9a3634d02301 ("arm64/sysreg: Convert CTR_EL0 to automatic generation")
Reported-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20220818213613.733091-4-broonie@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>