arm64: Reuse TCR field definitions for EL1 and EL2

TCR_EL1, TCR_EL2 and VTCR_EL2, all share some field positions
(TG0, ORGN0, IRGN0 and SH0) and their corresponding value definitions.

This patch makes the TCR_EL1 definitions reusable and uses them for TCR_EL2
and VTCR_EL2 fields.

This also fixes a bug where we assume TG0 in {V}TCR_EL2 is 1bit field.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>