compositor-drm: Refactor connector name into new function
compositor-drm: Refactor connector name into new function

Refactor the code constructing the connector name into a new function.
This makes create_output_for_connector() slightly easier to read.

Signed-off-by: Pekka Paalanen <0f6ae7001e34c37b02fb2c1c2573ddf8f442136a@collabora.co.uk>
Signed-off-by: Daniel Stone <62e7e355d5d8400fa8384448796af0bf6be4ffae@collabora.com>
Reviewed-by: Derek Foreman <2f97e0f0bc172406aab8ccd42dab54c95bab8759@osg.samsung.com>
Reviewed-by: Bryce Harrington <bdb14cfc1ab8d24e13de84adc40b41ae60c13bd1@osg.samsung.com>

eyolfson/weston,Fantu/compositor-spice,Fantu/compositor-spice,eyolfson/weston,jonnylamb/weston,Tarnyko/weston-xdg_surface_present,krezovic/weston,kwm81/weston,Gnurou/weston,Tarnyko/weston-xdg_surface_present,Fantu/compositor-spice,udoprog/weston,xorgy/weston,krezovic/weston,xorgy/weston,udoprog/weston,jonnylamb/weston,Gnurou/weston,sir-murray/weston,giucam/weston,giucam/weston,sir-murray/weston,kwm81/weston