staging: r8188eu: make ffaddr2pipehdl() static

The function ffaddr2pipehdl() is only used in usb_ops_linux.c.
Make it static.

Tested-by: Philipp Hortmann <philipp.g.hortmann@gmail.com> # Edimax N150
Signed-off-by: Michael Straube <straube.linux@gmail.com>
Link: https://lore.kernel.org/r/20220702064626.27506-1-straube.linux@gmail.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/r8188eu/include/usb_ops_linux.h

@@ -26,6 +26,4 @@
 #define usb_read_interrupt_complete(purb, regs)		\
 	usb_read_interrupt_complete(purb)
 
-unsigned int ffaddr2pipehdl(struct dvobj_priv *pdvobj, u32 addr);
-
 #endif

drivers/staging/r8188eu/os_dep/usb_ops_linux.c

@@ -7,7 +7,7 @@
 #include "../include/usb_ops_linux.h"
 #include "../include/rtl8188e_recv.h"
 
-unsigned int ffaddr2pipehdl(struct dvobj_priv *pdvobj, u32 addr)
+static unsigned int ffaddr2pipehdl(struct dvobj_priv *pdvobj, u32 addr)
 {
 	unsigned int pipe = 0, ep_num = 0;
 	struct usb_device *pusbd = pdvobj->pusbdev;