arm64: Enable EFI secret area Securityfs support

Enable EFI COCO secrets support. Provide the ioremap_encrypted() support required
by the driver.

Cc: Sami Mujawar <sami.mujawar@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@kernel.org>
Cc: Steven Price <steven.price@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>