usb: xhci: remove redundant variable 'erst_size'

'erst_size' represents the maximum capacity of entries that ERST can hold,
while 'num_entries' indicates the actual number of entries currently held
in the ERST. These two values are identical because the xhci driver does
not support ERST expansion. Thus, 'erst_size' is removed.

Suggested-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Niklas Neronin <niklas.neronin@linux.intel.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/20240429140245.3955523-7-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Epicurius

drivers/usb/host/xhci-dbgcap.c

@@ -516,7 +516,7 @@ static int xhci_dbc_mem_init(struct xhci_dbc *dbc, gfp_t flags)
 		goto string_fail;
 
 	/* Setup ERST register: */
-	writel(dbc->erst.erst_size, &dbc->regs->ersts);
+	writel(dbc->erst.num_entries, &dbc->regs->ersts);
 
 	lo_hi_writeq(dbc->erst.erst_dma_addr, &dbc->regs->erstba);
 	deq = xhci_trb_virt_to_dma(dbc->ring_evt->deq_seg,

drivers/usb/host/xhci.h

@@ -1376,8 +1376,6 @@ struct xhci_erst {
 	unsigned int		num_entries;
 	/* xhci->event_ring keeps track of segment dma addresses */
 	dma_addr_t		erst_dma_addr;
-	/* Num entries the ERST can contain */
-	unsigned int		erst_size;
 };
 
 struct xhci_scratchpad {