net/sonic: Fix CAM initialization

Section 4.3.1 of the datasheet says,

    This bit [TXP] must not be set if a Load CAM operation is in
    progress (LCAM is set). The SONIC will lock up if both bits are
    set simultaneously.

Testing has shown that the driver sometimes attempts to set LCAM
while TXP is set. Avoid this by waiting for command completion
before and after giving the LCAM command.

After issuing the Load CAM command, poll for !SONIC_CR_LCAM rather than
SONIC_INT_LCD, because the SONIC_CR_TXP bit can't be used until
!SONIC_CR_LCAM.

When in reset mode, take the opportunity to reset the CAM Enable
register.

Fixes: 1da177e4

 ("Linux-2.6.12-rc2")
Tested-by: Stan Johnson <userm57@yahoo.com>
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>