MIPS: VCT: Fix enabling of unwanted options if networking or USB support are disabled

MIPS: VCT: Fix enabling of unwanted options if networking or USB support are disabled

Some VCT boards lacks the support of networking or USB.
Additionally that support is disabled in small image
configurations.

If CONFIG_CMD_NET should not used the CONFIG_CMD_NFS option
have to be disabled too. Otherwise the linker fails with
unresolved symbols.

If CONFIG_VCT_SMALL_IMAGE is set than CONFIG_CMD_NET and
CONFIG_CMD_USB are disabled at the end of vct.h.
This is not adequate because CONFIG_CMD_USB enables additional
options and the linker fails again with unresolved symbols.

This patch adds an early check against CONFIG_VCT_SMALL_IMAGE
so the additional options are only enabled if they are really
needed.

Signed-off-by: Daniel Schwierzeck <daniel.schwierzeck@googlemail.com>
Acked-by: Stefan Roese <sr@denx.de>
Signed-off-by: Shinya Kuribayashi <skuribay@pobox.com>