drm/bridge: analogix-anx6345: Avoid duplicate -supply suffix

of_get_regulator() will unconditionally add "-supply" to form the
property name. This is documented in commit 69511a45

 ("map consumer
regulator based on device tree"). Remove the suffix from the requests.

Signed-off-by: Torsten Duwe <duwe@lst.de>
Reviewed-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20200218155440.BEFB968C65@verein.lst.de