nvmem: qfprom-sys: Add driver to export cell value

Add qfprom-sys driver to export the nvmem cell values as sysfs attrs to
enable user space access.

Change-Id: Ic1770054fe2a1b87cf56859aafba03f7340fe273
Signed-off-by: Naina Mehta <nainmeht@codeaurora.org>