shader: Use integer type for ARM (MALI GPU)

Currently, even the input/output buffers are integer formats, we still use float type for them. This is actually undefined behavior and MALI GPU will do type conversion and cause unexpected results. To fix this, we check the input buffer format for vertex shader and also color buffer format for fragment shader, if they are integer types, just use integer types in generated shaders. Since the old way works fine on other GPU, only enable this fix for ARM MALI.

Signed-off-by: Lepton Wu lepton@chromium.org