fbdev: da8xx-fb: remove incorrect type cast

The probe function correct passes a dma_addr_t pointer into
dma_alloc_coherent(), but has a cast to resource_size_t, which
might be different from dma_addr_t:

drivers/video/fbdev/da8xx-fb.c: In function 'fb_probe':
drivers/video/fbdev/da8xx-fb.c:1431:10: error: passing argument 3 of 'dma_alloc_coherent' from incompatible pointer type [-Werror=incompatible-pointer-types]

This removes the cast, which avoids the warning.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>