Fix warning:
symbol 'mpc5xxx_get_bus_frequency' was not declared. Should it be static?

Signed-off-by: Anatolij Gustschin <agust@denx.de>

With module.h being implicitly everywhere via device.h, the absence
of explicitly including something for EXPORT_SYMBOL went unnoticed.
Since we are heading to fix things up and clean module.h from the
device.h file, we need to explicitly include these files now.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

So far, MPC512x used mpc512x_find_ips_freq() to get the bus frequency,
while MPC52xx used mpc52xx_find_ipb_freq().  Despite the different
clock names (IPS vs. IPB) the code was identical.

Use common code for both processor families.

Signed-off-by: Wolfgang Denk <wd@denx.de>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>