be2net: do not modify PCI MaxReadReq size

Setting the PCI MRRS to a value of 4096 (overriding the system decided
value) had provided perf improvement in TX.
But, IBM has provided feedback that on POWER platforms, this value is set
by the system firmware, and drivers modifying this value can cause
unpredictable results (like EEH errors.) So, backing off this change.
On POWER7 platforms most slots, it seems, do get a MRRS of 4096.

This patch reverts the following commit:
"be2net: Modified PCI MaxReadReq size to 4096 bytes"
commit 5a56eb10.

Suggested-by: Brian King <bjking1@us.ibm.com>
Signed-off-by: Sathya Perla <sathya.perla@emulex.com>
Signed-off-by: David S. Miller <davem@davemloft.net>