ion: Don't allow building ION as a module.

ION doesn't export the proper symbols for it to be a module. This
causes build issues when ION is configured as a module.

Since Andorid kernels rarely use modules (I think recent policy
requires no modules?), go ahead and set the ION config to a bool
from the tristate option.

If folks decide ION as a module is important, we will have to go
through and export the various needed symbols.

Change-Id: I252ee445697c74c4269f6f589f41d72f095c95ff
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Git-commit: f2b94c52648fa1bb7cba053ab0f4a85e066485a1
Git-repo: http://android.googlesource.com/kernel/common/


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