[E1000]: Convert regtest macro's to functions

Minimal macro to function conversion in e1000_ethtool.c

Adds functions reg_pattern_test and reg_set_and_check
Changes REG_PATTERN_TEST and REG_SET_AND_CHECK macros
to call these functions.

Saves ~2.5KB

Compiled x86, untested (no hardware)

old:

$ size drivers/net/e1000/e1000_ethtool.o
   text    data     bss     dec     hex filename
  16778       0       0   16778    418a drivers/net/e1000/e1000_ethtool.o

new:

$ size drivers/net/e1000/e1000_ethtool.o
   text    data     bss     dec     hex filename
  14128       0       0   14128    3730 drivers/net/e1000/e1000_ethtool.o

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Auke Kok <auke-jan.h.kok@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>