video: fbdev: pmag-ba-fb: Remove bad `__init' annotation

Fix:

WARNING: drivers/video/fbdev/pmag-ba-fb.o(.text+0x308): Section mismatch in reference from the function pmagbafb_probe() to the function .init.text:pmagbafb_erase_cursor()
The function pmagbafb_probe()
references the function __init pmagbafb_erase_cursor().
This is often because pmagbafb_probe lacks a __init
annotation or the annotation of pmagbafb_erase_cursor is wrong.

-- a fallout from a missed update from commit 9625b513 ("VIDEO: 
PMAG-BA: Fix section mismatch") and then commit 48c68c4f ("Drivers: 
video: remove __dev* attributes.")

Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>