gallium/aux/tgsi_ureg.c: Fix various warnings

gallium/aux/tgsi_ureg.c: Fix various warnings

tgsi/tgsi_ureg.c: In function 'ureg_DECL_sampler':
tgsi/tgsi_ureg.c:721:34: warning: comparison between signed and unsigned
integer expressions [-Wsign-compare]
       if (ureg->sampler[i].Index == nr)
                                  ^~
tgsi/tgsi_ureg.c: In function 'match_or_expand_immediate64':
tgsi/tgsi_ureg.c:837:34: warning: unused parameter 'type' [-Wunused-
parameter]
                              int type,
                                  ^~~~
tgsi/tgsi_ureg.c: In function 'emit_decls':
tgsi/tgsi_ureg.c:1821:31: warning: comparison between signed and
unsigned integer expressions [-Wsign-compare]
       if (ureg->properties[i] != ~0)
                               ^~
tgsi/tgsi_ureg.c: In function 'ureg_create_with_screen':
tgsi/tgsi_ureg.c:2193:18: warning: comparison between signed and
unsigned integer expressions [-Wsign-compare]
    for (i = 0; i < ARRAY_SIZE(ureg->properties); i++)
                  ^

Signed-off-by: Gert Wollny <gert.wollny@collabora.com>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>