sungem: fix compile failure caused by trivial #include consolidation

Only Sparc and PPC actually have the asm/prom.h include and as such they
can't be moved outside of the ifdefs.
Reported-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/net/sungem.c

@@ -46,14 +46,15 @@
 #include <asm/byteorder.h>
 #include <asm/uaccess.h>
 #include <asm/irq.h>
-#include <asm/prom.h>
 
 #ifdef CONFIG_SPARC
 #include <asm/idprom.h>
+#include <asm/prom.h>
 #endif
 
 #ifdef CONFIG_PPC_PMAC
 #include <asm/pci-bridge.h>
+#include <asm/prom.h>
 #include <asm/machdep.h>
 #include <asm/pmac_feature.h>
 #endif