phy: mediatek: fix build warning of FIELD_PREP()

Change the inline function mtk_phy_update_field() into a macro to
avoid check warning of FIELD_PREP() with compiler parameter
-Wtautological-constant-out-of-range-compare

the warning is caused by mask check:
"BUILD_BUG_ON_MSG(__bf_cast_unsigned(_mask, _mask) >     \"

Fixes: 29c07477 ("phy: mediatek: add a new helper to update bitfield")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20220928070746.5393-1-chunfeng.yun@mediatek.com


Signed-off-by: Vinod Koul <vkoul@kernel.org>