r600: compare structure elements instead of doing a memcmp

r600: compare structure elements instead of doing a memcmp

Structures might be padded by the compiler and these padding bytes remain
un-initialized which in turn makes memcmp return a difference where from
the logical point of view there is none.

 Fixes valgrind:
     Conditional jump or move depends on uninitialised value(s)
       at 0x4C32CBA: __memcmp_sse4_1 (vg_replace_strmem.c:1099)
       by 0xB8D2537: r600_set_vertex_buffers (r600_state_common.c:573)
       by 0xB71D44A: u_vbuf_set_driver_vertex_buffers (u_vbuf.c:1129)
       by 0xB71F7BB: u_vbuf_draw_vbo (u_vbuf.c:1153)
       by 0xB3B92CB: st_draw_vbo (st_draw.c:235)
       by 0xB36B1AE: vbo_draw_arrays (vbo_exec_array.c:391)
       by 0xB36BB0D: vbo_exec_DrawArrays (vbo_exec_array.c:550)
       by 0x10A989: piglit_display (textureSize.c:157)
       by 0x4F8F174: run_test (piglit_fbo_framework.c:52)
       by 0x4F7BA12: piglit_gl_test_run (piglit-framework-gl.c:229)
       by 0x10A60A: main (textureSize.c:71)
     Uninitialised value was created by a stack allocation
       at 0xB3948FD: st_update_array (st_atom_array.c:388)

Signed-off-by: Gert Wollny <gert.wollny@collabora.com>
Reviewed-by: Roland Scheidegger <sroland@vmware.com>