net: qualcomm: make qca_7k_common a separate kernel module

In order to share common functions between QCA7000 SPI and UART protocol
driver the qca_7k_common needs to be a separate kernel module.

Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: David S. Miller <davem@davemloft.net>