Let the flash context directly point to the used master

We used to have a pointer to a full `registered_master` struct in
our flash context. Beside the used master, this contained a bit
mask of supported buses. Oddly convenient, this bit mask invited
to bypass the chip driver and break the abstraction. It allowed
to place bus-specific details virtually anywhere in flashprog,
making it harder to find a good place for them.

So, get rid of the `buses_supported` bit mask by pointing directly
to the master. Only the chip driver will implicitly know which type
of master is used.

Change-Id: I9ce13d8df0e7ccc67519d888dd9cb2e2ff8d6682
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.sourcearcade.org/c/flashprog/+/72533
diff --git a/pickit2_spi.c b/pickit2_spi.c
index a7b658e..9a0691e 100644
--- a/pickit2_spi.c
+++ b/pickit2_spi.c
@@ -202,7 +202,7 @@
 				     const unsigned char *writearr, unsigned char *readarr)
 {
 	const unsigned int total_packetsize = writecnt + readcnt + 20;
-	struct pickit2_spi_data *pickit2_data = flash->mst->spi.data;
+	struct pickit2_spi_data *pickit2_data = flash->mst.spi->data;
 
 	/* Maximum number of bytes per transaction (including command overhead) is 64. Lets play it safe
 	 * and always assume the worst case scenario of 20 bytes command overhead.