MAINTAINERS: fix reference to moved drivers/{misc => auxdisplay}/panel.c

Commit 51c1e9b554c9 ("auxdisplay: Move panel.c to drivers/auxdisplay folder")
moved the file, but the MAINTAINERS reference was not updated.

Link: https://lore.kernel.org/lkml/[e-mail]/
Reported-by: Joe Perches <[e-mail]>
Signed-off-by: Miguel Ojeda <[e-mail]>

MAINTAINERS

···
 M:	Ksenija Stanojevic <[e-mail]>
 S:	Odd Fixes
 F:	Documentation/auxdisplay/lcd-panel-cgram.txt
-F:	drivers/misc/panel.c
+F:	drivers/auxdisplay/panel.c
 
 PARALLEL PORT SUBSYSTEM
 M:	Sudip Mukherjee <[e-mail]>