video: xilinxfb: Use drvdata->regs_phys instead of physaddr

physaddr will be remove in the next patch.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>