de-constify opaque programmer struct

This removes const from opaque programmers so that we may change
their members at runtime, for example, if we want to change
max_data_read and max_data_write parameters.

BUG=none
BRANCH=pit
TEST=compile tested

Change-Id: I517aebf703ebca471d8c72e45386cf291a391dd8
Reviewed-on: https://gerrit.chromium.org/gerrit/61643
Reviewed-by: Yung-Chieh Lo <yjlou@chromium.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
Commit-Queue: David Hendricks <dhendrix@chromium.org>
Tested-by: David Hendricks <dhendrix@chromium.org>
diff --git a/programmer.h b/programmer.h
index 25f21fa..d9113cb 100644
--- a/programmer.h
+++ b/programmer.h
@@ -671,8 +671,8 @@
 	int (*erase) (struct flashchip *flash, unsigned int blockaddr, unsigned int blocklen);
 	const void *data;
 };
-extern const struct opaque_programmer *opaque_programmer;
-void register_opaque_programmer(const struct opaque_programmer *pgm);
+extern struct opaque_programmer *opaque_programmer;
+void register_opaque_programmer(struct opaque_programmer *pgm);
 
 /* serprog.c */
 #if CONFIG_SERPROG == 1