C: Fix atomic loads. [PR97981]

C: Fix atomic loads. [PR97981]

To handle atomic loads correctly, we need to move the code that
drops qualifiers in lvalue conversion after the code that
handles atomics.

2020-12-07  Martin Uecker  <muecker@gwdg.de>

gcc/c/
	PR c/97981
	* c-typeck.c (convert_lvalue_to_rvalue): Move the code
	that drops qualifiers to the end of the function.

gcc/testsuite/
	PR c/97981
	* gcc.dg/pr97981.c: New test.
	* gcc.dg/pr60195.c: Adapt test.