Remove CMDLINE from u8500-common

CMDLINE is not passed to the kernel here, at all, goodbye.

Also, we don't have bootloader, why not just put the only two valid reboot arguments?

And a reminder, delete the CFLAG DRECOVERY_CANT_USE_CONFIG_EXT4_FS_XATTR when SELinux is implemented anywhere else.

Change-Id: I6bcb4f7f0119213b5971e95eae5f1828c750343d
Move SELinux to common

@Paul-L
Update2