softpipe: pass surface format to get/put_tile functions

softpipe: pass surface format to get/put_tile functions

When we read/write image tiles we need to use the format specified
in the pipe_surface, not the pipe_transfer format (which comes from
the underlying texture/resource format).

This comes up when rendering to sRGB surfaces (via OpenGL render to
texture).  Ignoring the new GL_ARB/EXT_framebuffer_sRGB extension
for now, when we render to a sRGB surface we need to treat it like
a regular, linear colorspace RGB surface.  Before, when we read/wrote
tiles to sRGB surfaces we were inadvertantly doing the color space
conversion.