io_uring/register: guard compat syscall with CONFIG_COMPAT
Add compat.h include to avoid a potential build issue:
io_uring/register.c:281:6: error: call to undeclared function 'in_compat_syscall'; ISO C99 and later do not support implicit function declarations [-Werror,-Wimplicit-function-declaration]
if (in_compat_syscall()) {
^
1 warning generated.
io_uring/register.c:282:9: error: call to undeclared function 'compat_get_bitmap'; ISO C99 and later do not support implicit function declarations [-Werror,-Wimplicit-function-declaration]
ret = compat_get_bitmap(cpumask_bits(new_mask),
^
Fixes: c43203154d8a ("io_uring/register: move io_uring_register(2) related code to register.c") Reported-by: Manu Bretelle <chantra@meta.com> Reviewed-by: Jeff Moyer <jmoyer@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>