Print current MSR on printtrap(). Currently, printtrap just prints srr1, which
contains part of the MSR prior to the exception. I find useful to dump the
current value of the MSR, since it changes when there is an interruption.
With this patch, this is the new printtap model:
handled user trap:
exception = 0x700 (program) srr0 = 0x100008a0 (0x100008a0) srr1 = 0x800000000002f032 current msr = 0x8000000000009032 lr = 0x1000089c (0x1000089c) curthread = 0x7a50000 pid = 714, comm = ttrap2