soc: qcom: mem-buf: Improve modularity of certain functions

Certain functions in the mem-buf code assume that they will
operate on a particular type of structure that houses all of
the information that they need. This becomes restrictive
when attempting to use those functions without the housing
data structure. Thus, to improve the modularity of these
functions, change their signatures so that they require
only the necessary pieces of information as inputs.

Change-Id: I93c988f700fed3db5a5ccf8702cb8ac100f8f428
Signed-off-by: Isaac J. Manjarres <isaacm@codeaurora.org>