LU-2327 ptlrpc: Print spinlock owner information

If CONFIG_DEBUG_SPINLOCK is enabled, the spinlock owner and magic values
are now printed in the "spinning too long" message.

Signed-off-by: Prakash Surya <surya1@llnl.gov>
Change-Id: Ib9e13833e5a67d03792edd8eaee519493ba50c9e