drm/nouveau: mark nv_printk_ as printf-like function

...and fix all warnings

Signed-off-by: Marcin Slusarz <marcin.slusarz@gmail.com>
drm/nouveau/bios: tiny debugging messages fixes

COPY_ZM_REG: destination and source addresses were swapped
RAM_RESTRICT_ZM_REG_GROUP: missing 0x prefix for register address

Signed-off-by: Marcin Slusarz <marcin.slusarz@gmail.com>