ARM: OMAP2: Fix missing omap2xxx_clkt_vps_late_init function calls

During the migration to the common clock framework, calls to the
functions omap2xxx_clkt_vps_late_init() were not preserved for
OMAP2420 and OMAP2430. This causes the variables "sys_ck_rate" and
"curr_prcm_set" to be uninitialised on boot. On reboot, this causes the
following error message to be displayed because the appropriate MPU
clock frequency (derived from sys_ck_rate) cannot be found.

"Could not set MPU rate to 4294MHz"

Fix this by adding back calls to omap2xxx_clkt_vps_late_init() in the
OMAP2420 and OMAP2430 clock initialisation code.

Signed-off-by: Jon Hunter <jon-hunter@ti.com>
[paul@pwsan.com: dropped the duplicated call to
 omap2xxx_clkt_vps_check_bootloader_rates() after consultation with Jon;
 updated patch description]
Signed-off-by: Paul Walmsley <paul@pwsan.com>