[POWERPC] arch/powerpc/platforms/iseries/pci.c: Use time_* macros

The functions time_before, time_before_eq, time_after, and
time_after_eq are more robust for comparing jiffies against other
values.

This implements usage of the time_after() macro, defined at
linux/jiffies.h, which deals with wrapping correctly.

Signed-off-by: S.Çağlar Onur <caglar@pardus.org.tr>
Acked-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>