spi: Pass master instead of flash to .send_command

In the SPI-master API, `.send_command` should only forward commands to
the SPI bus. All details about the commands and the SPI slave should be
handled in the chip driver. Hence, replace the `flashctx` pointer with
one to the `spi_master` to enforce proper separation.

Change-Id: I50934a1294217794b7e23cc98ade7e4279c059a1
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.sourcearcade.org/c/flashprog/+/74897
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
diff --git a/serprog.c b/serprog.c
index 6cf87f0..257562a 100644
--- a/serprog.c
+++ b/serprog.c
@@ -356,7 +356,7 @@
 	return 0;
 }
 
-static int serprog_spi_send_command(const struct flashctx *flash,
+static int serprog_spi_send_command(const struct spi_master *,
 				    unsigned int writecnt, unsigned int readcnt,
 				    const unsigned char *writearr,
 				    unsigned char *readarr);
@@ -989,7 +989,7 @@
 	sp_prev_was_write = 0;
 }
 
-static int serprog_spi_send_command(const struct flashctx *flash,
+static int serprog_spi_send_command(const struct spi_master *mst,
 				    unsigned int writecnt, unsigned int readcnt,
 				    const unsigned char *writearr,
 				    unsigned char *readarr)