lib: asn1_decoder - add MODULE_LICENSE("GPL")

A kernel taint results when loading the rsa_generic module:

root@(none):~# modprobe rsa_generic
asn1_decoder: module license 'unspecified' taints kernel.
Disabling lock debugging due to kernel taint

"Tainting" of the kernel is (usually) a way of indicating that
a proprietary module has been inserted, which is not the case here.
Signed-off-by: Tudor Ambarus <tudor-dan.ambarus@nxp.com>
Signed-off-by: David Howells <dhowells@redhat.com>

lib/asn1_decoder.c

@@ -12,6 +12,7 @@
 #include <linux/export.h>
 #include <linux/kernel.h>
 #include <linux/errno.h>
+#include <linux/module.h>
 #include <linux/asn1_decoder.h>
 #include <linux/asn1_ber_bytecode.h>
 
@@ -504,3 +505,5 @@ int asn1_ber_decoder(const struct asn1_decoder *decoder,
 	return -EBADMSG;
 }
 EXPORT_SYMBOL_GPL(asn1_ber_decoder);
+
+MODULE_LICENSE("GPL");