mesa: fix OES_texture_float texture render target behavior

mesa: fix OES_texture_float texture render target behavior

Current implementation allowed usage of unsized type texture GL_FLOAT
and GL_HALF_FLOAT as a render target as this was 'expected behavior' by
WEBGL_oes_texture_float and is also allowed by the oes-texture-float
WebGL test. However this broke some ES3 conformance tests that do not
accept such behavior. Patch sets such an fbo incomplete as expected by
the ES3 conformance tests. Textures with sized types like RGBA32F will
still continue to work as render targets.

v2: code style cleanups (Ian Romanick, Matt Turner)

Signed-off-by: Tapani Pälli <tapani.palli@intel.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=88905
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Cc: "10.5" <mesa-stable@lists.freedesktop.org>