omap: rpmsg: bump to max freq while booting remote processor

Reduce the remote processor booting time by bumping to the max
frequency. This is achieved by putting in constraints before
the loading of the remote processor. The latter is known through
the RPROC_PRELOAD notification.

Once the remote processor has reached a certain point, it would
send a message, RP_MSG_BOOTINIT_DONE via mailbox to notify the
host that the remote processor has completed the basic boot and
initization. The constraints are released upon receipt of this
message. They are also released in case of an error during
loading.

NOTE: The current implementation used tput api for ipu since
freq scale api is not supported directly yet.

Change-Id: I1fe936087f00872756c7b532ee58d923e695ff28
Signed-off-by: Miguel Vadillo <vadillo@ti.com>
Signed-off-by: Fernando Guzman Lugo <fernando.lugo@ti.com>
Signed-off-by: Subramaniam C.A <subramaniam.ca@ti.com>
Signed-off-by: Chandra Sekhar.Anagani <chandu@ti.com>
Signed-off-by: Suman Anna <s-anna@ti.com>

Conflicts:

	arch/arm/plat-omap/omap_rpmsg.c