twl6030 battery: pass nominal capacity from board file

Pass the nominal battery capacity from the board file instead of
hardcoding it in the driver.

TODO: This needs to be done for the blaze as well, although it's
rarely run off the battery

Change-Id: I15cba65f062c70f3b1e26f3c03db59e3af0d6ea9
Signed-off-by: Sivakumar Pothireddy <sivakumar.pothireddy@ti.com>
Signed-off-by: Anand Gadiyar <gadiyar@ti.com>