Switch the sh7372 CPU support to use CMT2 instead
of CMT1 for system timer.

CMT1 is located in the A3SP power domain while CMT2
is located in the always-on power domain C5.

This improves our PM situation - with CMT2 as timer
we can power down A3SP and still access the timer.
Signed-off-by: NMagnus Damm <damm@opensource.se>
Signed-off-by: NPaul Mundt <lethal@linux-sh.org>