powerpc/tm: Update function prototype comment

In commit eb5c3f1c ("powerpc: Always save/restore checkpointed regs
during treclaim/trecheckpoint") __tm_recheckpoint was modified to no
longer take the second parameter 'unsigned long orig_msr' as part of a
TM rewrite to simplify the reclaiming/recheckpointing process.

There is a comment in the asm file where the function is delcared which
has an incorrect prototype with the 'orig_msr' parameter.

This patch corrects the comment.

Signed-off-by: Cyril Bur <cyrilbur@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>