ibm_newemac: select CRC32 in Kconfig

The ibm_newemac driver requires ether_crc to be defined.  Apparently it is
possible to generate a .config without CONFIG_CRC32 set which causes the
following link errors if IBM_NEW_EMAC is selected:

  LD      .tmp_vmlinux1
drivers/built-in.o: In function `emac_hash_mc':
core.c:(.text+0x2f524): undefined reference to `crc32_le'
core.c:(.text+0x2f528): undefined reference to `bitrev32'
make: *** [.tmp_vmlinux1] Error 1

This patch has IBM_NEW_EMAC select CRC32 so we don't hit this error.

Signed-off-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>