partition: DOS: Add parameter for the NT disk Signature
The NT disk Signature is a unique 32-bit value in the MBR allowing
to identify a MSDOS partitioned disk. The signature can be used to
specify the Linux rootfs.
This patch adds support for the NT disk Signature in the form of a
device parameter which can both be read and written.
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>