xtensa: remove the get_order() implementation

xtensa: remove the get_order() implementation

As the get_order() implemented by xtensa supporting 'nsau'
instruction seems be the same as the generic implementation
in include/asm-generic/getorder.h when size is not a constant
value as the generic implementation calling the fls*() is also
utilizing the 'nsau' instruction for xtensa.

So remove the get_order() implemented by xtensa, as using the
generic implementation may enable the compiler to do the
computing when size is a constant value instead of runtime
computing and enable the using of get_order() in BUILD_BUG_ON()
macro in next patch.

CC: Andrew Morton <akpm@linux-foundation.org>
CC: Linux-MM <linux-mm@kvack.org>
Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
Acked-by: Max Filippov <jcmvbkbc@gmail.com>
Reviewed-by: Alexander Duyck <alexanderduyck@fb.com>
Link: https://patch.msgid.link/20241028115343.3405838-6-linyunsheng@huawei.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>