wifi: mt76: mt7915: drop always true condition of __mt7915_reg_addr()

smatch warnings:
addr <= MT_CBTOP2_PHY_END(0xffffffff) is always true (<= u32max),
so drop it.

Fixes: cd4c314a

 ("mt76: mt7915: refine register definition")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Ryder Lee <ryder.lee@mediatek.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>