RNDIS function has a limitation on the number of allowed instances.
So far it has been RNDIS_MAX_CONFIGS, which happens to be one.
In order to eliminate this kind of arbitrary limitation we should not
preallocate a predefined (RNDIS_MAX_CONFIGS) array of struct rndis_params
instances but instead allow allocating them on demand.

This patch prepares the elimination of the said limit by converting all the
functions which accept rndis config number to accept a pointer to the
actual struct rndis_params. Consequently, rndis_register() returns
a pointer to a corresponding struct rndis_params instance. The pointer
is then always used by f_rndis.c instead of config number when it talks
to rndis.c API.

A nice side-effect of the changes is that many lines of code in rndis.c
become shorter and fit in 80 columns.

If a function prototype changes in rndis.h a style cleanup is made
at the same time, otherwise checkpatch complains that the patch
has style problems.
Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@samsung.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>