devmouse is not always needed; move it to amd64/core.json

Signed-off-by: Ronald G. Minnich <rminnich@gmail.com>

sys/src/9/amd64/core.json

@@ -75,6 +75,7 @@
 			"ctype.c",
 			"devarch.c",
 			"../port/devdraw.c",
+			"../port/devmouse.c",
 			"../port/devpci.c",
 			"devpmc.c",
 			"fpu.c",

sys/src/9/port/port.json

@@ -27,7 +27,6 @@
 			"../port/devkbin.c",
 			"../port/devmnt.c",
 			"../port/devmntn.c",
-			"../port/devmouse.c",
 			"../port/devpipe.c",
 			"../port/devproc.c",
 			"../port/devregress.c",