stm32f1x: add more asserts

this at least checks the post conditions after convoluted code.

Change-Id: Idfa8cbedce5288d8bae5743687949f141dfb07b2
Signed-off-by: Øyvind Harboe <oyvind.harboe@zylin.com>
Reviewed-on: http://openocd.zylin.com/187
Tested-by: jenkins
Reviewed-by: Andreas Fritiofson <andreas.fritiofson@gmail.com>

src/flash/nor/stm32f1x.c

@@ -1107,9 +1107,15 @@ static int stm32x_probe(struct flash_bank *bank)
 
 	LOG_INFO("flash size = %dkbytes", num_pages);
 
+	/* did we assign # of pages? */
+	assert(num_pages != 0xffff);
+
 	/* calculate numbers of pages */
 	num_pages /= (page_size / 1024);
 
+	/* check that calculation result makes sense */
+	assert(num_pages > 0);
+
 	if (bank->sectors)
 	{
 		free(bank->sectors);