net: davinci_emac: Fix incorrect masking of tx and rx error channel

The bit-masks used for the TXERRCH and RXERRCH (tx and rx error channels)
are incorrect and always lead to a zero result. The mask values are
currently the incorrect post-right shifted values, fix this by setting
them to the currect values.

(I double checked these against the TMS320TCI6482 data sheet, section
5.30, page 127 to ensure I had the correct mask values for the TXERRCH
and RXERRCH fields in the MACSTATUS register).

Addresses-Coverity: ("Operands don't affect result")
Fixes: a6286ee6

 ("net: Add TI DaVinci EMAC driver")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>