soc: Driver to access and modify device CSRs.

commit f62d36e0dc6337e9bd378ba31e2f31f28cc27d5d from
git@git.assembla.com:cavium/WindRiver.linux.git

A character driver which implements read and write ioctls so
that a user space utitlity can either read from or write a new
value to OcteonTx2 or OcteonTx3 HW device config registers.

Change-Id: Ie59e855e4ae473a69f893fcfeef975da4becefdd
Signed-off-by: Rakesh Babu <rsaladi2@marvell.com>
Reviewed-on: https://sj1git1.cavium.com/c/IP/SW/kernel/linux/+/47364


Reviewed-by: Sunil Kovvuri Goutham <Sunil.Goutham@cavium.com>
Tested-by: Sunil Kovvuri Goutham <Sunil.Goutham@cavium.com>
Signed-off-by: Ruiqiang Hao <Ruiqiang.Hao@windriver.com>