southbridge/amd/agesa/hudson: Clean up AGESA #includes

Just like in commit
* 1d87dac hp/pavilion_m6_1035dx: Sanitize #includes

Include AGESA headers specifying the path relative to AGESA_ROOT. The
path is specified relative to AGESA_ROOT as opposed to src/ since this
code may include headers from different AGESA families, depending on
the board.

Change-Id: Ide38cc34e207a8b617d1d319fd9c17a785f55833
Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
Reviewed-on: http://review.coreboot.org/5423
Tested-by: build bot (Jenkins)
Reviewed-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Reviewed-by: Idwer Vollering <vidwer@gmail.com>

src/southbridge/amd/agesa/hudson/spi.c

@@ -26,7 +26,7 @@
 #include <device/pci_ops.h>
 
 #if defined (CONFIG_HUDSON_IMC_FWM)
-#include "FchPlatform.h"
+#include <Proc/Fch/FchPlatform.h>
 
 static int bus_claimed = 0;
 #endif