ion: Improve ION config description

Mostly just to quiet checkpatch warnings, be more verbose
in describing the ION config option.

Change-Id: I194235f1a68623dca15ae6e658fc99d00943a827
Signed-off-by: John Stultz <john.stultz@linaro.org>
Git-commit: 8f1c42284159ebd6851e1e75507f2ad6fba87d0f
Git-repo: http://android.googlesource.com/kernel/common/


Signed-off-by: Mitchel Humpherys <mitchelh@codeaurora.org>