spi25: Introduce generic spi_prepare_io()/spi_finish_io()

Introduce two new functions to be hooked up in the chip database:
* spi_prepare_io(), and
* spi_finish_io().

These will be used to prepare multi-i/o and QPI operations. Hence,
hook them up to all the chips that support those. spi_prepare_4ba()
is wrapped to account for overlaps with 4BA support.

Change-Id: I444f6322b6d6a26a040cb0ca972b2c411838d702
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.sourcearcade.org/c/flashprog/+/163
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
diff --git a/include/chipdrivers.h b/include/chipdrivers.h
index 272b65c..94db44b 100644
--- a/include/chipdrivers.h
+++ b/include/chipdrivers.h
@@ -61,7 +61,8 @@
 int spi_set_extended_address(struct flashctx *, uint8_t addr_high);
 
 /* spi25_prepare.c */
-int spi_prepare_4ba(struct flashctx *, enum preparation_steps);
+int spi_prepare_io(struct flashctx *, enum preparation_steps);
+void spi_finish_io(struct flashctx *);
 
 
 /* spi25_statusreg.c */