xtensa: fix __sync_fetch_and_{and,or}_4 declarations

Building xtensa kernel with gcc-10 produces the following warnings:
  arch/xtensa/kernel/xtensa_ksyms.c:90:15: warning: conflicting types
    for built-in function ‘__sync_fetch_and_and_4’;
    expected ‘unsigned int(volatile void *, unsigned int)’
    [-Wbuiltin-declaration-mismatch]
  arch/xtensa/kernel/xtensa_ksyms.c:96:15: warning: conflicting types
    for built-in function ‘__sync_fetch_and_or_4’;
    expected ‘unsigned int(volatile void *, unsigned int)’
    [-Wbuiltin-declaration-mismatch]

Fix declarations of these functions to avoid the warning.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>