st/mesa: fix wrong comparison in update_framebuffer_state()

st/mesa: fix wrong comparison in update_framebuffer_state()

state_tracker/st_atom_framebuffer.c:208:27: warning: comparison of constant 4294967295 with expression of type 'uint16_t' (aka 'unsigned short') is always false [-Wtautological-constant-out-of-range-compare]
   if (framebuffer->width == UINT_MAX)
       ~~~~~~~~~~~~~~~~~~ ^  ~~~~~~~~
state_tracker/st_atom_framebuffer.c:210:28: warning: comparison of constant 4294967295 with expression of type 'uint16_t' (aka 'unsigned short') is always false [-Wtautological-constant-out-of-range-compare]
   if (framebuffer->height == UINT_MAX)
       ~~~~~~~~~~~~~~~~~~~ ^  ~~~~~~~~
2 warnings generated.

Fixes: eb0fd0e5f86 ("gallium: decrease the size of pipe_framebuffer_state - 96 -> 80 bytes")
Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Brian Paul <brianp@vmware.com>