c: Handle initializations of opaque types [PR106016]

c: Handle initializations of opaque types [PR106016]

The initial commit that added opaque types thought that there couldn't
be any valid initializations for variables of these types, but the test
case in the bug report shows that isn't true.  The solution is to handle
OPAQUE_TYPE initializations like the other scalar types.

2022-06-17  Peter Bergner  <bergner@linux.ibm.com>

gcc/
	PR c/106016
	* expr.cc (count_type_elements): Handle OPAQUE_TYPE.

gcc/testsuite/
	PR c/106016
	* gcc.target/powerpc/pr106016.c: New test.

(cherry picked from commit 975658b782f36dcf6eb190966d5b705977bfd5eb)