[Patch][libgomp] Add 'gcn' to oacc-init.c's name_of_acc_device_t

[Tobias Burnus]

While investigating some other failure, I saw that 'gcn' was missing 
from that function. – It is only used in the error case and I failed to 
trigger it in a quick way. – Hence, only compiled and regtested w/o 
triggering this issue. If needed be, I can try harder, though.

OK?
Tobias

PS: On the OG9 branch, there is a stub for 
_acc_device_hsa/_acc_device_intel_mic (but not on trunk) – but in this 
function, those fall through to 'default:'.

2019-11-15  Tobias Burnus  <tob...@codesourcery.com>

	libgomp/
	* oacc-init.c (name_of_acc_device_t): Handle acc_device_gcn.

diff --git a/libgomp/oacc-init.c b/libgomp/oacc-init.c
index e1568c535b3..adc159e60b9 100644
--- a/libgomp/oacc-init.c
+++ b/libgomp/oacc-init.c
@@ -103,6 +103,7 @@ name_of_acc_device_t (enum acc_device_t type)
     case acc_device_host: return "host";
     case acc_device_not_host: return "not_host";
     case acc_device_nvidia: return "nvidia";
+    case acc_device_gcn: return "gcn";
     default: gomp_fatal ("unknown device type %u", (unsigned) type);
     }
 }