opengl/gltexture: Fix format for 565 textures
GL_INVALID_OPERATION is generated if type is one of [...] GL_UNSIGNED_SHORT_5_6_5, GL_UNSIGNED_SHORT_5_6_5_REV, [...] and format is not GL_RGB.
(cherry picked from commit 60e39643)
GL_INVALID_OPERATION is generated if type is one of [...] GL_UNSIGNED_SHORT_5_6_5, GL_UNSIGNED_SHORT_5_6_5_REV, [...] and format is not GL_RGB.
(cherry picked from commit 60e39643)