const'ify flashctx to align signatures with cros flashrom

The ChromiumOS flashrom fork has since const'ify flashctx
in a few places. This aligns the function signatures to
match with downstream to ease forward porting patches
out of downstream back into mainline flashrom.

This patch is minimum viable alignment and so feedback is
welcome.

Change-Id: Iff6dbda13cb0d941481c0d204b9c30895630fbd1
Signed-off-by: Edward O'Callaghan <quasisec@google.com>
Original-Reviewed-on: https://review.coreboot.org/c/flashrom/+/40324
Original-Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/flashrom-stable/+/70933
Reviewed-by: Nico Huber <nico.h@gmx.de>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/wbsio_spi.c b/wbsio_spi.c
index f4f6af9..1674825 100644
--- a/wbsio_spi.c
+++ b/wbsio_spi.c
@@ -57,7 +57,7 @@
 	return flashport;
 }
 
-static int wbsio_spi_send_command(struct flashctx *flash, unsigned int writecnt,
+static int wbsio_spi_send_command(const struct flashctx *flash, unsigned int writecnt,
 				  unsigned int readcnt,
 				  const unsigned char *writearr,
 				  unsigned char *readarr);
@@ -110,7 +110,7 @@
  * Would one more byte of RAM in the chip (to get all 24 bits) really make
  * such a big difference?
  */
-static int wbsio_spi_send_command(struct flashctx *flash, unsigned int writecnt,
+static int wbsio_spi_send_command(const struct flashctx *flash, unsigned int writecnt,
 				  unsigned int readcnt,
 				  const unsigned char *writearr,
 				  unsigned char *readarr)