msm: RPM: Add debugfs support to send requests to RPM

A debugfs directory called "rpm_send_msg" is created for the user
to be able to send RPM messages.

The user should fill in the message with all the required fields.
These fields are to be seperated by " ". The set, resource type
and the key parameters are to passed as strings.

The fields are as follows:
set - active set or sleep set
resource_type: type of the resource
resourse_id: identifies a resource within a type
nelems: no of key-value pairs (maximum of 20)
key - key for a corresponding data
data - frequency

Example entry -" echo sleep clk0 1 1 KHz 120000 > message "

Change-Id: I4d8690ccdac8943e04d70c0406f55be26f63d931
Signed-off-by: Deepak Katragadda <dkatraga@codeaurora.org>