net: sh_eth: Convert cache operations to static functions

net: sh_eth: Convert cache operations to static functions

Turn the current cache operation macros into static functions to improve
compiler coverage checking. This does change the driver behavior slightly,
the driver now expects those cache operation functions to be available on
all architectures on which it is used. This should pose no problem, as the
driver is only used on 32bit and 64bit ARM, which both have those operations.
The CFG_SH_ETHER_ALIGNE_SIZE is converted to SH_ETHER_ALIGN_SIZE and defined
as either 64 on ARM or 16 on SH.

Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>