xhci: Clean up xhci_{alloc,free}_erst() declarations

xhci_alloc_erst() has global scope even though it's only used in
xhci-mem.c.  Declare it static.

xhci_free_erst() was removed by commit b17a57f8 ("xhci: Refactor
interrupter code for initial multi interrupter support."), but a
declaration in xhci.h still remains.  Drop it.
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/20231019102924.2797346-12-mathias.nyman@linux.intel.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/host/xhci-mem.c

@@ -1776,7 +1776,7 @@ void xhci_free_command(struct xhci_hcd *xhci,
 	kfree(command);
 }
 
-int xhci_alloc_erst(struct xhci_hcd *xhci,
+static int xhci_alloc_erst(struct xhci_hcd *xhci,
 		    struct xhci_ring *evt_ring,
 		    struct xhci_erst *erst,
 		    gfp_t flags)

drivers/usb/host/xhci.h

@@ -2048,13 +2048,8 @@ struct xhci_ring *xhci_ring_alloc(struct xhci_hcd *xhci,
 void xhci_ring_free(struct xhci_hcd *xhci, struct xhci_ring *ring);
 int xhci_ring_expansion(struct xhci_hcd *xhci, struct xhci_ring *ring,
 		unsigned int num_trbs, gfp_t flags);
-int xhci_alloc_erst(struct xhci_hcd *xhci,
-		struct xhci_ring *evt_ring,
-		struct xhci_erst *erst,
-		gfp_t flags);
 void xhci_initialize_ring_info(struct xhci_ring *ring,
 			unsigned int cycle_state);
-void xhci_free_erst(struct xhci_hcd *xhci, struct xhci_erst *erst);
 void xhci_free_endpoint_ring(struct xhci_hcd *xhci,
 		struct xhci_virt_device *virt_dev,
 		unsigned int ep_index);