fbdev/metronomefb: Use hardware device for dev_err()

Replace the use of the fbdev software device, stored in struct
fb_info.dev, with the hardware device from struct fb_info.device
in load_waveform(). The device is only used for printing errors
with dev_err().

This change aligns load_waveform() with the rest of the driver and
prepares fbdev for making struct fb_info.dev optional.

Signed-off-by: Thomas Zimmermann <[e-mail]>
Reviewed-by: Javier Martinez Canillas <[e-mail]>
Reviewed-by: Sam Ravnborg <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/video/fbdev/metronomefb.c

···
 	int mem_idx = 0;
 	struct waveform_hdr *wfm_hdr;
 	u8 *metromem = par->metromem_wfm;
-	struct device *dev = par->info->dev;
+	struct device *dev = par->info->device;
 
 	if (user_wfm_size)
 		epd_frame_table[par->dt].wfm_size = user_wfm_size;