arm64/efi: Move uaccess en/disable out of efi_set_pgd()

arm64/efi: Move uaccess en/disable out of efi_set_pgd()

efi_set_pgd() will no longer be called when invoking EFI runtime
services via the efi_rts_wq work queue, but the uaccess en/disable are
still needed when using PAN emulation using TTBR0 switching. So move
these into the callers.

Acked-by: Will Deacon <will@kernel.org>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>