ipmi: Cleanup DEBUG_TIMING ifdef usage

ipmi: Cleanup DEBUG_TIMING ifdef usage

The driver uses #ifdef DEBUG_TIMING in order to conditionally print out
timestamped debug messages. Unfortunately it adds the ifdefs all over the
usage sites.

This patch cleans it up by adding a debug_timestamp() function which
is compiled out if DEBUG_TIMING isn't present. This cleans up all
the ugly ifdefs in the function logic.

Cc: [email protected]
Cc: Arnd Bergmann <[email protected]>
Signed-off-by: John Stultz <[email protected]>
Signed-off-by: Corey Minyard <[email protected]>