amdgcn: Fix expansion of GCN_BUILTIN_LDEXPV builtin

2022-11-08  Kwok Cheung Yeung  <kcy@codesourcery.com>

	gcc/
	* config/gcn/gcn.cc (gcn_expand_builtin_1): Expand first argument
	of GCN_BUILTIN_LDEXPV to V64DFmode.