Consider count_in in Noux terminal-read function

It does not suffice to constrain the amount of returned data with chunk
size of the transport buffer because the client may have specified an
even smaller value. For example, libreadline reads single characters
from the terminal and expects a single character in return. A different
amount is interpreted as EOF.

ports/src/noux/terminal_io_channel.h

@@ -64,9 +64,12 @@ namespace Noux {
 				return false;
 			}
 
-			Genode::size_t count = terminal.read(sysio->read_out.chunk,
-			                                     sizeof(sysio->read_out.chunk));
-			sysio->read_out.count = count;
+			Genode::size_t const max_count =
+				Genode::min(sysio->read_in.count,
+				            sizeof(sysio->read_out.chunk));
+
+			sysio->read_out.count =
+				terminal.read(sysio->read_out.chunk, max_count);
 			return true;
 		}