sfc: add new headers in preparation for code split

New headers contain prototypes of functions that will be common between
ef10 and upcoming driver.
Removed static modifier from the affected functions.
Some function prototypes were removed from existing headers.

Signed-off-by: Alexandru-Mihai Maftei <amaftei@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>