arm64/sysreg: Get rid of TRFCR_ELx SysregFields

There is no such thing as TRFCR_ELx in the architecture.
What we have is TRFCR_EL1, for which TRFCR_EL12 is an accessor.

Rename TRFCR_ELx_* to TRFCR_EL1_*, and fix the bit of code using
these names.

Similarly, TRFCR_EL12 is redefined as a mapping to TRFCR_EL1.

Reviewed-by: James Clark <james.clark@linaro.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/87cygsqgkh.wl-maz@kernel.org
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Will Deacon <will@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>