stm32lx: don't allow part_info to be uninitialized

It's possible for us to fail to read the part ID code so make sure that
part_info is initialized to NULL before attempting to do so, otherwise
we could proceed and use it uninitialized and then segfault.

Change-Id: I0a3f3d3947690b66f0981b5046340449521e0b33
Signed-off-by: Jack Peel <jack.peel@synapse.com>
Signed-off-by: Andrey Yurovsky <yurovsky@gmail.com>
Reviewed-on: http://openocd.zylin.com/2276
Reviewed-by: Andreas Fritiofson <andreas.fritiofson@gmail.com>
Tested-by: jenkins
Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>

src/flash/nor/stm32lx.c

@@ -214,7 +214,7 @@ FLASH_BANK_COMMAND_HANDLER(stm32lx_flash_bank_command)
 		return ERROR_COMMAND_SYNTAX_ERROR;
 
 	/* Create the bank structure */
-	stm32lx_info = malloc(sizeof(struct stm32lx_flash_bank));
+	stm32lx_info = calloc(1, sizeof(*stm32lx_info));
 
 	/* Check allocation */
 	if (stm32lx_info == NULL) {
@@ -624,6 +624,7 @@ static int stm32lx_probe(struct flash_bank *bank)
 	uint32_t second_bank_base;
 
 	stm32lx_info->probed = 0;
+	stm32lx_info->part_info = NULL;
 
 	int retval = stm32lx_read_id_code(bank->target, &device_id);
 	if (retval != ERROR_OK)