MIPS: cpu-bugs64: Mark inline functions as __always_inline

Commit ac7c3e4f ("compiler: enable CONFIG_OPTIMIZE_INLINING
forcibly") allows compiler to uninline functions marked as 'inline'.
Leading to section mismatch in this case.

Since we're using const variables to pass assembly flags, 'inline's
can't be dropped. So we simply mark them as __always_inline.

Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Cc: linux-mips@vger.kernel.org
[paul.burton@mips.com:
  - Annotate these functions with __init, even if it only serves to
    inform human readers when the code can be used.
  - Drop the __always_inline from check_daddi() & check_daddiu() which
    don't use arguments as immediates in inline asm.
  - Rewrap the commit message.]
Signed-off-by: Paul Burton <paul.burton@mips.com>