drm/panel: ltk050h3146w: use dev_err_probe wherever possible

This is only a cosmetic change.

This replaces a hand-crafted EPROBE_DEFER handling for deciding to print
an error message with dev_err_probe.

A side-effect is that dev_err_probe also adds a debug message when it's
not EPROBE_DEFER, but this is seen as an improvement.

Cc: Quentin Schulz <foss+kernel@0leil.net>
Signed-off-by: Quentin Schulz <quentin.schulz@theobroma-systems.com>
Reviewed-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20240104-ltk-dev_err_probe-v1-2-8ef3c0b585d8@theobroma-systems.com