[MIPS] Bring the SWARM defconfig up to date

 The SWARM defconfig file has not been regenerated for over a year now.
Here is a patch to bring the file up to date.  Additionally some important
and sometimes confusing changes happened meanwhile.  Here is the list of
notable corresponding updates to the configuration:

1. CPU_SB1_PASS_2_2 is now selected rather than CPU_SB1_PASS_1.  The
   latter requires a non-standard -msb1-pass1-workarounds option to be
   supported by GCC and I am told is quite rare anyway.

   [Ralf: Afaik -msb1-pass1-workarounds is available only in Monta Vista's
   special Sibyte gcc 3.0 variant and gcc 3.0 is too old to build a modern
   kernel anyway.]

2. PHYLIB and BROADCOM_PHY are both built in and NETDEV_1000 enabled as
   required by SB1250_MAC.

3. USB and USB_OHCI_HCD are enabled as there is an OHCI chip onboard.

4. TMPFS is enabled, because I use it. ;-)
Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>