gpu: ion: Fix bug in heap type enum

Change-Id: I8bf1345896774f02bd25c8d25a05d2c1eae262ef
Signed-off-by: Rebecca Schultz Zavin <rebecca@android.com>
[mitchelh@codeaurora.org: manually applied to renamed file due to broken
rename detection since we never deleted include/linux/ion.h. Also, one
fixup due to whitespace differences.]
Signed-off-by: Mitchel Humpherys <mitchelh@codeaurora.org>