gallium: Add PIPE_CAP_SURFACE_REINTERPRET_BLOCKS

gallium: Add PIPE_CAP_SURFACE_REINTERPRET_BLOCKS

This cap indicates whether pipe->create_surface can reinterpret a texture
as a surface with a format of different block width/height (but equal
block size).

v2: fix whitespace

Reviewed-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>