southbridge/amd/pi/hudson: Fix HUDSON_DISABLE_IMC kconfig warning

Platforms selecting the HUDSON_DISABLE_IMC symbol were showing the
warning:

warning: (BOARD_SPECIFIC_OPTIONS && BOARD_SPECIFIC_OPTIONS &&
CPU_AMD_AGESA_BINARY_PI) selects HUDSON_DISABLE_IMC which has unmet
direct dependencies (SOUTHBRIDGE_AMD_PI_AVALON ||
SOUTHBRIDGE_AMD_PI_BOLTON || SOUTHBRIDGE_AMD_PI_KERN)

By moving the definition of the symbol outside of the if block
and removing the default n, we can get rid of the warning without
changing the value for any platform.

Change-Id: I5c1bdfbcf3c5c44ee05b8c5e679f6854d784d8dc
Signed-off-by: Martin Roth <gaumless@gmail.com>
Reviewed-on: http://review.coreboot.org/10680
Tested-by: build bot (Jenkins)
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Idwer Vollering <vidwer@gmail.com>
1 file changed