arm64: asm-offsets: remove MM_CONTEXT_ID

The only user of the MM_CONTEXT_ID defintion was removed in commit:

  25b92693 ("arm64: mm: convert cpu_do_switch_mm() to C")

Remove MM_CONTEXT_ID.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20241007123921.549340-5-mark.rutland@arm.com


Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>