lnwallet: fix constant overflow build issue on 32-bit systems

This commit fixes a build issue that appears when attempting to
cross-compile binaries to a 32-bit system from a 64-bit system. The
issue was that the defined max-state hint overflows a 32-bit integer. To
fix this issue, we now proeprly specify a type of a uint64 for the typed
constant.

lnwallet/script_utils.go

@@ -46,7 +46,7 @@ const (
 	// maxStateHint is the maximum state number we're able to encode using
 	// StateHintSize bytes amongst the sequence number and locktime fields
 	// of the commitment transaction.
-	maxStateHint = (1 << 48) - 1
+	maxStateHint uint64 = (1 << 48) - 1
 )
 
 // witnessScriptHash generates a pay-to-witness-script-hash public key script