i915: Fix type of "specoffset" variable.

Commit 2e5a1a2 (intel: Convert from GLboolean to 'bool' from
stdbool.h.) converted the "specoffset" local variable (in
intel_tris.c) from a GLboolean to a bool.  However, GLboolean was the
wrong type for specoffset--it should have been a GLuint (to match the
declaration of specoffset in struct intel_context).

This patch changes specoffset to the proper type.

Fixes piglit test general/two-sided-lighting-separate-specular.

This is a candidate for stable branches.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=45917
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

src/mesa/drivers/dri/i915/intel_tris.c

@@ -663,7 +663,7 @@ do {							\
    struct intel_context *intel = intel_context(ctx);			\
    GLuint color[n] = { 0, }, spec[n] = { 0, };				\
    GLuint coloroffset = intel->coloroffset;				\
-   bool specoffset = intel->specoffset;				\
+   GLuint specoffset = intel->specoffset;				\
    (void) color; (void) spec; (void) coloroffset; (void) specoffset;