MIPS: Alchemy: update development boards defconfigs with USB platform drivers

Commit 2be350fa (MIPS: Alchemy: use the ehci platform driver) and commit
e223a4cc (MIPS: Alchemy: use the OHCI platform driver) have change the Alchemy
platform code to register an EHCI and OHCI platform driver, the defconfig file
must thus be accordingly updated to build these drivers by default.

Signed-off-by: Florian Fainelli <florian@openwrt.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>