gallium/util: get h264 level based on number of max references and resolution
gallium/util: get h264 level based on number of max references and resolution

v2: add commments for limitation of max references numbers,
and what the caculation is based

Signed-off-by: Leo Liu <2cc5244297c0b82e7ea531cc4a868153602775b7@amd.com>
Reviewed-by: Christian König <c7ea837d7a46effe4232b086213468b8b31643bf@amd.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler