eepro100: Use symbolic names and BIT macros in binary operations

eepro100: Use symbolic names and BIT macros in binary operations

Instead of magic numbers like 0x8000, symbolic names are used
for the SCB command and status bits.

There are too many configuration bits to use symbolic names
there, too. Using the BIT macro is a little help when comparing
code and documentation.

For the same reason, some other constants were replaced by
the BITS macro.

Signed-off-by: Stefan Weil <weil@mail.berlios.de>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>