spi_flash: support old STMicro parts with RES

Some old STMicro parts do not support JEDEC ID (0x9f). This patch
uses RES (0xab) to get Electronic ID and translates it to JEDEC ID.

Signed-off-by: Thomas Chou <thomas@wytron.com.tw>
Acked-by: Mike Frysinger <vapier@gentoo.org>