mount: support filesystem options passed via -o ...

Similar to mount(8) the barebox command mount now supports passing a string
to the file system driver via -o.

This is used in the next commit to let the user specify port numbers for
nfs mounts.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

Cleanup Kconfig files ...

This patch provides a global cleanup barebox Kconfig files. This includes
replacing spaces to tabs, formatting in accordance format.
No functional changes.

Signed-off-by: Alexander Shiyan <shc_work@mail.ru>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

introduce common bootstrap code ...

This will allow to have a generic code to create different bootstrap

As example
Barebox as TI Xloader
Barebox as AT91 Bootstrap

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>