openmp: Fix up handling of DECL_OMP_PRIVATIZED_MEMBER for bit-fields [PR95063]

The r11-15 change broke this testcase, as it now asserts type is equal to
the type of the DECL_VALUE_EXPR, but for DECL_OMP_PRIVATIZED_MEMBER artificial
vars mapping to bitfields it wasn't.  Fixed by changing the
DECL_OMP_PRIVATIZED_MEMBER var type in that case.

2020-05-12  Jakub Jelinek  <jakub@redhat.com>

	PR c++/95063
	* pt.c (tsubst_decl): Deal with DECL_OMP_PRIVATIZED_MEMBER for
	a bit-field.

	* g++.dg/gomp/pr95063.C: New test.