st/omx: count number of slices
st/omx: count number of slices

Used by nouveau driver.
Similar patch was done for st/va:
851e7e12aa628d6781b5a3af2f2fc16ee73f435f

Signed-off-by: Julien Isorce <2904e845d63d102574cbb95a4bcdefac0a5d7af0@samsung.com>
Reviewed-by: Christian König <c7ea837d7a46effe4232b086213468b8b31643bf@amd.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler