libsel4utils: IA32: Squash compiler warnings.

GCC 5.3.1 warns that these variables are used uninitialised. The cause is that
they are provided to an `asm` block as inputs despite not actually being inputs
to the contained `asm`. This commit silences these warnings reducing confusion
in a project build.

libsel4utils/src/process.c

diff --git a/libsel4utils/src/process.c b/libsel4utils/src/process.c
index 173821a..e166d9b 100644
--- a/libsel4utils/src/process.c
+++ b/libsel4utils/src/process.c
@@ -106,7 +106,7 @@
 seL4_CPtr
 sel4utils_mint_cap_to_process(sel4utils_process_t *process, cspacepath_t src, seL4_CapRights rights, seL4_CapData_t data)
 {
-    cspacepath_t dest;
+    cspacepath_t dest = { 0 };
     if (next_free_slot(process, &dest) == -1) {
         return 0;
     }
@@ -125,7 +125,7 @@
 seL4_CPtr
 sel4utils_copy_cap_to_process(sel4utils_process_t *process, cspacepath_t src)
 {
-    cspacepath_t dest;
+    cspacepath_t dest = { 0 };
     if (next_free_slot(process, &dest) == -1) {
         return 0;
     }
@@ -144,7 +144,7 @@
 seL4_CPtr
 sel4utils_move_cap_to_process(sel4utils_process_t *process, cspacepath_t src, vka_t *from_vka)
 {
-    cspacepath_t dest;
+    cspacepath_t dest = { 0 };
     if (next_free_slot(process, &dest) == -1) {
         return 0;
     }