u_vbuf: Make sure all caps are initialized
u_vbuf: Make sure all caps are initialized

Pointed out by valgrind.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=83148
Reviewed-by: Alex Deucher <08dc22c6156113f2deff178e35e3ed9b24d6af9e@amd.com>

djreep81/glsl-optimizer,dellis1972/glsl-optimizer,zz85/glsl-optimizer,zz85/glsl-optimizer,djreep81/glsl-optimizer,tokyovigilante/glsl-optimizer,dellis1972/glsl-optimizer,metora/MesaGLSLCompiler,dellis1972/glsl-optimizer,bkaradzic/glsl-optimizer,tokyovigilante/glsl-optimizer,bkaradzic/glsl-optimizer,zz85/glsl-optimizer,dellis1972/glsl-optimizer,bkaradzic/glsl-optimizer,djreep81/glsl-optimizer,benaadams/glsl-optimizer,wolf96/glsl-optimizer,wolf96/glsl-optimizer,bkaradzic/glsl-optimizer,jbarczak/glsl-optimizer,benaadams/glsl-optimizer,djreep81/glsl-optimizer,tokyovigilante/glsl-optimizer,wolf96/glsl-optimizer,jbarczak/glsl-optimizer,benaadams/glsl-optimizer,jbarczak/glsl-optimizer,metora/MesaGLSLCompiler,wolf96/glsl-optimizer,mcanthony/glsl-optimizer,zeux/glsl-optimizer,benaadams/glsl-optimizer,zeux/glsl-optimizer,benaadams/glsl-optimizer,mcanthony/glsl-optimizer,mcanthony/glsl-optimizer,mcanthony/glsl-optimizer,zz85/glsl-optimizer,jbarczak/glsl-optimizer,zeux/glsl-optimizer,jbarczak/glsl-optimizer,dellis1972/glsl-optimizer,djreep81/glsl-optimizer,benaadams/glsl-optimizer,wolf96/glsl-optimizer,zz85/glsl-optimizer,mcanthony/glsl-optimizer,bkaradzic/glsl-optimizer,tokyovigilante/glsl-optimizer,tokyovigilante/glsl-optimizer,zz85/glsl-optimizer,metora/MesaGLSLCompiler,zeux/glsl-optimizer,zeux/glsl-optimizer