Active map and ROI map use unsigned rows/cols
Active map and ROI map use unsigned rows/cols

The vpx_roi_map_t and vpx_active_map_t structures use unsigned rows
and cols but VP8_COMMON uses signed values for mb_rows and mb_cols.

Cleans warning in Android build:
comparison of integers of different signs: 'int' and 'unsigned int'
if (cpi->common.mb_rows != rows || cpi->common.mb_cols != cols)
    ~~~~~~~~~~~~~~~~~~~ ^  ~~~~
comparison of integers of different signs: 'int' and 'unsigned int'
if (cpi->common.mb_rows != rows || cpi->common.mb_cols != cols)
                                   ~~~~~~~~~~~~~~~~~~~ ^  ~~~~
comparison of integers of different signs: 'unsigned int' and 'int'
if (rows == cpi->common.mb_rows && cols == cpi->common.mb_cols)
    ~~~~ ^  ~~~~~~~~~~~~~~~~~~~
comparison of integers of different signs: 'unsigned int' and 'int'
if (rows == cpi->common.mb_rows && cols == cpi->common.mb_cols)

Change-Id: If1f118c20ffefd2530fbd371e6787cc8a6c31f0a

luctrudeau/aom,smarter/aom,Topopiccione/libvpx,ShiftMediaProject/libvpx,mbebenita/aom,Topopiccione/libvpx,mbebenita/aom,luctrudeau/aom,Topopiccione/libvpx,mwgoldsmith/vpx,smarter/aom,GrokImageCompression/aom,Topopiccione/libvpx,smarter/aom,mbebenita/aom,mwgoldsmith/vpx,GrokImageCompression/aom,ShiftMediaProject/libvpx,ShiftMediaProject/libvpx,GrokImageCompression/aom,smarter/aom,mbebenita/aom,luctrudeau/aom,mwgoldsmith/libvpx,GrokImageCompression/aom,mbebenita/aom,smarter/aom,GrokImageCompression/aom,webmproject/libvpx,mwgoldsmith/libvpx,Topopiccione/libvpx,webmproject/libvpx,webmproject/libvpx,GrokImageCompression/aom,mwgoldsmith/vpx,luctrudeau/aom,ShiftMediaProject/libvpx,mbebenita/aom,Topopiccione/libvpx,webmproject/libvpx,mbebenita/aom,mwgoldsmith/libvpx,mwgoldsmith/libvpx,mwgoldsmith/vpx,luctrudeau/aom,webmproject/libvpx,mwgoldsmith/vpx,mbebenita/aom,ShiftMediaProject/libvpx,luctrudeau/aom,mwgoldsmith/libvpx,mbebenita/aom,mwgoldsmith/vpx,mwgoldsmith/libvpx,webmproject/libvpx,smarter/aom