msm: pil-q6v5-mss: Fix device tree style problems with is_loadable

The device tree spec allows for the use of boolean parameter
types. Use this boolean type for the is_loadable parameter.
Also rename the parameter to "is-loadable" (use a hyphen
instead of the underscore).

Change-Id: I4895021bbab95d6fb256feb05854445fdf65f55f
Signed-off-by: Vikram Mulukutla <markivx@codeaurora.org>