compiler: fix check for notinheap conversion
A normal pointer may not be converted to a notinheap pointer. We were
erroneously permitting a conversion from a normal pointer to a
notinheap unsafe.Pointer, which is useless since unsafe.Pointer is not
marked notinheap. Correct the test to permit a conversion from
unsafe.Pointer to a notinheap pointer, which is the same test that the
gc compiler uses.
The test case for this is in the 1.9 runtime package.
Reviewed-on: https://go-review.googlesource.com/62731
git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@252745 138bc75d-0d04-0410-961f-82ee72b054a4