arm64: mm: place __cpu_setup in .text

We drop __cpu_setup in .text.init, which ends up being part of .text.
The .text.init section was a legacy section name which has been unused
elsewhere for a long time.

The ".text.init" name is misleading if read as a synonym for
".init.text". Any CPU may execute __cpu_setup before turning the MMU on,
so it should simply live in .text.

Remove the pointless section assignment. This will leave __cpu_setup in
the .text section.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>