nir: Fix a comment typo in nir_lower_drawpixels.
nir: Fix a comment typo in nir_lower_drawpixels.

Reviewed-by: Rob Clark <915c10c999604870200b6defbe633d857c856ca0@gmail.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler