arm64: introduce mov_q macro to move a constant into a 64-bit register

Implement a macro mov_q that can be used to move an immediate constant
into a 64-bit register, using between 2 and 4 movz/movk instructions
(depending on the operand)

Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
(cherry picked from commit 30b5ba5cf333cc650e474eaf2cc1ae91bc7cf89f)
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>