stringlist-functions: add sorted insert ...

Add sorted insert in stringlist functions.
Also added function to checked if string is already
in string list.

Signed-off-by: Alexander Aring <a.aring@phytec.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

list: remove duplicated list.h ...

We accidently have two list implementations in the tree:
include/list.h and include/linux/list.h. This patch moves
the latter (newer one) to include/linux/list.h.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

add stringlist function. They can be used to build a list ...

of strings. For now mainly useful to print the resulting
list in columns which is used in tab completion and ls.