sh_eth: fix misreporting of transmit abort

Due to obviously missing braces, EESR.TABT (transmit abort) interrupt may be
reported even if it hasn't happened, just when EESR.TWB (transmit descriptor
write-back) interrupt happens. Luckily (?), EESR.TWB is disabled by the driver
via the TRIMD register and all the interrupt masks, so that transmit abort is
never actually logged...

Put the braces where they should be and fix the incoherent comment, while at it.

Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: David S. Miller <davem@davemloft.net>