arm64: mm: Remove MAX_USER_VA_BITS definition

arm64: mm: Remove MAX_USER_VA_BITS definition

commit 9b31cf493ffa ("arm64: mm: Introduce MAX_USER_VA_BITS definition")
introduced the MAX_USER_VA_BITS definition, which was used to support
the arm64 mm use-cases where the user-space could use 52-bit virtual
addresses whereas the kernel-space would still could a maximum of 48-bit
virtual addressing.

But, now with commit b6d00d47e81a ("arm64: mm: Introduce 52-bit Kernel
VAs"), we removed the 52-bit user/48-bit kernel kconfig option and hence
there is no longer any scenario where user VA != kernel VA size
(even with CONFIG_ARM64_FORCE_52BIT enabled, the same is true).

Hence we can do away with the MAX_USER_VA_BITS macro as it is equal to
VA_BITS (maximum VA space size) in all possible use-cases. Note that
even though the 'vabits_actual' value would be 48 for arm64 hardware
which don't support LVA-8.2 extension (even when CONFIG_ARM64_VA_BITS_52
is enabled), VA_BITS would still be set to a value 52. Hence this change
would be safe in all possible VA address space combinations.

Cc: James Morse <james.morse@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Steve Capper <steve.capper@arm.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: linux-kernel@vger.kernel.org
Cc: kexec@lists.infradead.org
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Bhupesh Sharma <bhsharma@redhat.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>