video: fbdev: don't print error message on platform_get_irq() failure

The platform_get_irq() can print error message, so remove the redundant
dev_err() here.

Signed-off-by: Tang Bin <tangbin@cmss.chinamobile.com>
Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200406053450.8380-1-tangbin@cmss.chinamobile.com