tg3: Invert nvram_read() and nvram_read_swab()

This patch removes the blind byteswap of NVRAM data as it is read in.
To preserve the logic at the call sites, this patch also inverts every
call to tg3_nvram_read() and tg3_nvram_read_swab().  The call swap gets
confusing within tg3_nvram_read_le() (LE is a misnomer), but the reader
should be able to convince himself / herself that the resulting behavior
is still unchanged.

Signed-off-by: Matt Carlson <mcarlson@broadcom.com>
Signed-off-by: Benjamin Li <benli@broadcom.com>
Signed-off-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>