arm64: mm: Remove split_p*d() functions

Since the efi_create_mapping() no longer generates block mappings
and being the last user of the split_p*d code, remove these functions
and the corresponding TLBI.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
[ardb: replace 'overlapping regions' with 'block mappings' in commit log]
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>