[AX.25]: Make asc2ax() thread-proof

Asc2ax was still using a static buffer for all invocations which isn't
exactly SMP-safe.  Change asc2ax to take an additional result buffer as
the argument.  Change all callers to provide such a buffer.

This one only really is a fix for ROSE and as per recent discussions
there's still much more to fix in ROSE ...

Signed-off-by: Ralf Baechle DL5RB <ralf@linux-mips.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/rose/rose_subr.c b/net/rose/rose_subr.c
index 02891ce..36a7794 100644
--- a/net/rose/rose_subr.c
+++ b/net/rose/rose_subr.c
@@ -337,13 +337,13 @@
 				memcpy(&facilities->source_addr, p + 7, ROSE_ADDR_LEN);
 				memcpy(callsign, p + 12,   l - 10);
 				callsign[l - 10] = '\0';
-				facilities->source_call = *asc2ax(callsign);
+				asc2ax(&facilities->source_call, callsign);
 			}
 			if (*p == FAC_CCITT_SRC_NSAP) {
 				memcpy(&facilities->dest_addr, p + 7, ROSE_ADDR_LEN);
 				memcpy(callsign, p + 12, l - 10);
 				callsign[l - 10] = '\0';
-				facilities->dest_call = *asc2ax(callsign);
+				asc2ax(&facilities->dest_call, callsign);
 			}
 			p   += l + 2;
 			n   += l + 2;