[PATCH] cs5535_gpio.c: call cdev_del() during module_exit to unmap kobject references and other cleanups

During module unloading, cdev_del() must be called to unmap cdev related
kobject references and other cleanups(such as inode->i_cdev being set to
NULL) which prevents the OOPS upon subsequent loading, usage and unloading
of modules(as seen in the mail thread
http://marc.theaimsgroup.com/?l=linux-kernel&m=114533640609018&w=2).

Also, remove unneeded test of gpio_base.
Signed-off-by: Thayumanavar Sachithanantham <thayumk@gmail.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>