loader: tslog: Add more log for module loading

This helps mesuring what's happening when we load the kernel/modules/mfsroot.

This also adds TSENTER2 which uses the third argument of TSRAW, same
as in the kernel.

MFC after: 2 weeks
Sponsored by: Beckhoff Automation GmbH & Co. KG
Differential Revision: https://reviews.freebsd.org/D33699

(cherry picked from commit 01cad731921bb60b4f6e04c1cac987eea7af9d08)