net: synquacer: Add netsec driver

Add SynQuacer's NETSEC GbE controller driver.
Since this driver will load the firmware from SPI NOR flash,
this depends on CONFIG_SYNQUACER_SPI=y.

Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>
Reviewed-by: Ramon Fried <rfried.dev@gmail.com>