renderthread: relax error handling for wide gamut EGL configs

It is valid to advertise EGL_EXT_pixel_format_float, but not have a
the requested EGL config. Instead of aborting, fallback to the default
behavior.

Change-Id: I6c602233b627dc2070364434fece57d3d0aab435
Cc: Romain Guy <romainguy@google.com>
Signed-off-by: Rob Herring <robh@kernel.org>