opaque: Move probing into PREPARE_POST_PROBE hook

To get rid of the flash context in probing, we have to split the
detection of chip parameters out into a preparation step. Below
the opaque-master API, things could actually stay as they are,
we rename `.probe` to `.prepare` though for completeness.

Change-Id: Ic8418e6c5bdc49f5133cdb21efed0bf6dc2f820e
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.sourcearcade.org/c/flashprog/+/449
diff --git a/flashchips.c b/flashchips.c
index dbcb11f..6a99456 100644
--- a/flashchips.c
+++ b/flashchips.c
@@ -27371,6 +27371,7 @@
 		},
 		.write		= write_opaque,
 		.read		= read_opaque,
+		.prepare_access	= prepare_opaque,
 	},
 
 	{