Add ASN.1 ENUMERATED tag support

Add ASN.1 ENUMERATED [1] tag to supported tag list.

1. https://tools.ietf.org/html/rfc3641#page-8

Signed-off-by: Mykhailo Sopiha <mykhailo.sopiha@linaro.org>
diff --git a/library/asn1write.c b/library/asn1write.c
index a138d0b..b3a3ad5 100644
--- a/library/asn1write.c
+++ b/library/asn1write.c
@@ -231,7 +231,7 @@
     return( (int) len );
 }
 
-int mbedtls_asn1_write_int( unsigned char **p, unsigned char *start, int val )
+static int asn1_write_tagged_int( unsigned char **p, unsigned char *start, int val, int tag )
 {
     int ret;
     size_t len = 0;
@@ -255,11 +255,21 @@
     }
 
     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) );
-    MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_INTEGER ) );
+    MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, tag ) );
 
     return( (int) len );
 }
 
+int mbedtls_asn1_write_int( unsigned char **p, unsigned char *start, int val )
+{
+    return( asn1_write_tagged_int( p, start, val, MBEDTLS_ASN1_INTEGER ) );
+}
+
+int mbedtls_asn1_write_enum( unsigned char **p, unsigned char *start, int val )
+{
+    return( asn1_write_tagged_int( p, start, val, MBEDTLS_ASN1_ENUMERATED ) );
+}
+
 int mbedtls_asn1_write_tagged_string( unsigned char **p, unsigned char *start, int tag,
     const char *text, size_t text_len )
 {