build: remove unused variables

detected by clang.

Change-Id: Id9effcc5437870f37fecd33803f7753c6eca53d6
Signed-off-by: Spencer Oliver <spen@spen-soft.co.uk>
Reviewed-on: http://openocd.zylin.com/361
Tested-by: jenkins
Reviewed-by: Øyvind Harboe <oyvindharboe@gmail.com>
Reviewed-by: Mathias Küster <kesmtp@freenet.de>

src/flash/nor/str7x.c

@@ -726,12 +726,10 @@ static int str7x_write(struct flash_bank *bank, uint8_t *buffer,
 		/* data word 1 */
 		target_write_memory(target, str7x_get_flash_adr(bank, FLASH_DR0),
 				4, 1, last_dword);
-		bytes_written += 4;
 
 		/* data word 2 */
 		target_write_memory(target, str7x_get_flash_adr(bank, FLASH_DR1),
 				4, 1, last_dword + 4);
-		bytes_written += 4;
 
 		/* start programming cycle */
 		cmd = FLASH_DWPG | FLASH_WMS;