arm/mem_access: Add and cleanup (TCR_|TTBCR_)* defines

arm/mem_access: Add and cleanup (TCR_|TTBCR_)* defines

This commit adds (TCR_|TTBCR_)* defines to simplify access to the
respective register contents. At the same time, we adjust the macros
TCR_T0SZ and TCR_TG0_* by using the newly introduced TCR_T0SZ_SHIFT and
TCR_TG0_SHIFT instead of the hardcoded values.

Signed-off-by: Sergej Proskurin <proskurin@sec.in.tum.de>
Acked-by: Julien Grall <julien.grall@arm.com>
Signed-off-by: Stefano Stabellini <sstabellini@kernel.org>