Remove a direct include of rwlock.h which fail on a kernel with the RT patches

Remove a direct include of rwlock.h which fail on a kernel with the RT patches

The file linux/rwlock.h should not be included directly as stated by
an #error message at the 5th line of the file. With a RT patched
kernel, linux/rwlock_rt.h should be included instead of linux/rwlock.h.
The file linux/spinlock.h already do the proper check. We then should
let the include be done by this file.

Signed-off-by: Raphaël Beamonte <raphael.beamonte@gmail.com>
Signed-off-by: Yannick Brosseau <yannick.brosseau@gmail.com>