Add units to the timing information, so we know that the numbers are
nanoseconds.  The output changes from:

I/O      : 165 (172)
attribute: 300 (316)
common   : 300 (316)

to:

I/O      : 165ns (172ns)
attribute: 300ns (316ns)
common   : 300ns (316ns)
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>