st_glsl_to_tgsi: bump index back up to 32-bit

with some of the fp64 emulation, we are seeing shaders coming in with
> 32K temps, they go out with 40 or so used, but while doing register
renumber we need to store a lot of them.

So bump this fields back up to 32-bit.

Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

src/mesa/state_tracker/st_glsl_to_tgsi.cpp

@@ -165,7 +165,7 @@ public:
 
    explicit st_src_reg(st_dst_reg reg);
 
-   int16_t index; /**< temporary index, VERT_ATTRIB_*, VARYING_SLOT_*, etc. */
+   int32_t index; /**< temporary index, VERT_ATTRIB_*, VARYING_SLOT_*, etc. */
    int16_t index2D;
    uint16_t swizzle; /**< SWIZZLE_XYZWONEZERO swizzles from Mesa. */
    int negate:4; /**< NEGATE_XYZW mask from mesa */
@@ -239,7 +239,7 @@ public:
 
    explicit st_dst_reg(st_src_reg reg);
 
-   int16_t index; /**< temporary index, VERT_ATTRIB_*, VARYING_SLOT_*, etc. */
+   int32_t index; /**< temporary index, VERT_ATTRIB_*, VARYING_SLOT_*, etc. */
    int16_t index2D;
    gl_register_file file:5; /**< PROGRAM_* from Mesa */
    unsigned writemask:4; /**< Bitfield of WRITEMASK_[XYZW] */