parlib: Fix context detection in __prep_sighandler()

In commit f3f00eeae350 ("parlib: Fix aggressively-saved FP state for
signals"), we were checking the wrong context.  If the uthread was not
saved, its context was in VCPD.  That's why we have the ctx variable.

Signed-off-by: Barret Rhoden <brho@cs.berkeley.edu>

user/parlib/signal.c

diff --git a/user/parlib/signal.c b/user/parlib/signal.c
index e8d2351..4680411 100644
--- a/user/parlib/signal.c
+++ b/user/parlib/signal.c
@@ -163,7 +163,7 @@
 	uthread->sigstate.data = (struct sigdata*)stack;
 	/* Parlib aggressively saves the FP state for HW and VM ctxs.  SW ctxs
 	 * should not have FP state saved. */
-	switch (uthread->u_ctx.type) {
+	switch (ctx->type) {
 	case ROS_HW_CTX:
 	case ROS_VM_CTX:
 		assert(uthread->flags & UTHREAD_FPSAVED);