LOCAL / fbdev: bcm2708_fb: fix build warnings on 64bit build

LOCAL / fbdev: bcm2708_fb: fix build warnings on 64bit build

There are build warnings on arm64 build. Fix following build
warnings:
   drivers/video/fbdev/bcm2708_fb.c: In function 'vc_mem_copy':
   drivers/video/fbdev/bcm2708_fb.c:507:49: warning: format '%d' expects argument of type 'int', but argument 3 has type 'size_t {aka long unsigned int}' [-Wformat=]
      pr_err("[%s]: failed to dma_alloc_coherent(%d)\n",
                                                    ^
   drivers/video/fbdev/bcm2708_fb.c:516:22: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
      unsigned char *p = (unsigned char *)ioparam.src + offset;
                         ^
   drivers/video/fbdev/bcm2708_fb.c: In function 'bcm2708_fb_probe':
   drivers/video/fbdev/bcm2708_fb.c:844:9: warning: format '%x' expects argument of type 'unsigned int', but argument 2 has type 'dma_addr_t {aka long long unsigned int}' [-Wformat=]
     pr_info("BCM2708FB: allocated DMA memory %08x\n",
            ^~~~~~

This only fixes the warnings, but functionality of fb_dmacopy is
already broken on ARM64.

Change-Id: Ib9035e38c79e668f74b47139c2a39faf937226db
Signed-off-by: Seung-Woo Kim <sw0312.kim@samsung.com>