misc: fix ti-st build issues

st_drv uses skb*() interfaces, so it should depend on NET.
It also uses GPIO interfaces, so it should depend on GPIOLIB.

st_kim.c uses syss_*() calls, so it should #include
<linux/sysfs.h>.

Fixes these observed build errors:
ERROR: "skb_queue_purge" [drivers/misc/ti-st/st_drv.ko] undefined!
ERROR: "skb_pull" [drivers/misc/ti-st/st_drv.ko] undefined!
ERROR: "skb_queue_tail" [drivers/misc/ti-st/st_drv.ko] undefined!
ERROR: "__alloc_skb" [drivers/misc/ti-st/st_drv.ko] undefined!
ERROR: "kfree_skb" [drivers/misc/ti-st/st_drv.ko] undefined!
ERROR: "skb_dequeue" [drivers/misc/ti-st/st_drv.ko] undefined!
ERROR: "skb_put" [drivers/misc/ti-st/st_drv.ko] undefined!

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Pavan Savoy <pavan_savoy@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>