msm: mdss: add a fb type for fb mmap ioctl

Using fb mmap, we can get a buffer from ion handle,
or from a fixed adress physical continuous memory.
Earlier if mmap is called more than once then ion
handle won't be NULL and fb would allocate using
physical continuous memory. Fix this to ensure the
type of fb allocation is correct by storing fb map
type.

Change-Id: I2b47b08b7fcb06f8220fcfe8852f5c2e37ade628
Signed-off-by: Mao Flynn <Flynn@codeaurora.org>
Signed-off-by: Jayant Shekhar <jshekhar@codeaurora.org>