arch/xtensa: always_inline get_current() and current_thread_info()

Mark get_current() and current_thread_info() functions as always_inline to
fix the following modpost warning:

WARNING: modpost: vmlinux: section mismatch in reference: get_current+0xc (section: .text.unlikely) -> initcall_level_names (section: .init.data)

The warning happens when these functions are called from an __init
function and they don't get inlined (remain in the .text section) while
the value they return points into .init.data section.  Assuming
get_current() always returns a valid address, this situation can happen
only during init stage and accessing .init.data from .text section during
that stage should pose no issues.

Link: https://lkml.kernel.org/r/20240704132506.1011978-2-surenb@google.com
Fixes: 22d407b1

 ("lib: add allocation tagging support for memory allocation profiling")
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Cc: Chris Zankel <chris@zankel.net>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: kernel test robot <lkp@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>