carminefb: Fix module parameters permissions

The third parameter of module_param is supposed to be an octal value.
The missing leading "0" causes the following:

$ ls -l /sys/module/carminefb/parameters/
total 0
-rw-rwxr-- 1 root root 4096 Jul  8 08:55 fb_displays
-rw-rwxr-- 1 root root 4096 Jul  8 08:55 fb_mode
-rw-rwxr-- 1 root root 4096 Jul  8 08:55 fb_mode_str

After fixing the perm parameter, we get the expected:

$ ls -l /sys/module/carminefb/parameters/
total 0
-r--r--r-- 1 root root 4096 Jul  8 08:56 fb_displays
-r--r--r-- 1 root root 4096 Jul  8 08:56 fb_mode
-r--r--r-- 1 root root 4096 Jul  8 08:56 fb_mode_str

Signed-off-by: Jean Delvare <jdelvare@suse.de>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: stable@kernel.org
Signed-off-by: Paul Mundt <lethal@linux-sh.org>