snmpapi: Constify a variable

[Andrew Talbot]

Changelog:
    snmpapi: Constify a variable.

diff --git a/dlls/snmpapi/main.c b/dlls/snmpapi/main.c
index 3686ed9..62e9ab3 100644
--- a/dlls/snmpapi/main.c
+++ b/dlls/snmpapi/main.c
@@ -32,7 +32,7 @@
 
 WINE_DEFAULT_DEBUG_CHANNEL(snmpapi);
 
-static INT asn_any_copy(AsnAny *dst, AsnAny *src)
+static INT asn_any_copy(AsnAny *dst, const AsnAny *src)
 {
     memset(dst, 0, sizeof(AsnAny));
     switch (src->asnType)