bnx2: Replace open-coded byte swapping with swab32s()

Read NVRAM directly into buffer and use swab32s() to byte swap it in-place
instead of reading it into the end of the buffer and swapping it manually
while copying it.

[bhelgaas: commit log]
Link: https://lore.kernel.org/r/e4ac6229-1df5-8760-3a87-1ad0ace87137@gmail.com


Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>