[gas] Update .loc syntax comment in dwarf2dbg.c

I noticed that a comment in gas/dwarf2dbg.c describing .loc syntax was missing
the "view VALUE" option.

Fix this by adding the missing option.

gas/dwarf2dbg.c

diff --git a/gas/dwarf2dbg.c b/gas/dwarf2dbg.c
index 05f9662..f04f297 100644
--- a/gas/dwarf2dbg.c
+++ b/gas/dwarf2dbg.c
@@ -25,7 +25,7 @@
 	.file FILENO "file.c"
 	.loc  FILENO LINENO [COLUMN] [basic_block] [prologue_end] \
 	      [epilogue_begin] [is_stmt VALUE] [isa VALUE] \
-	      [discriminator VALUE]
+	      [discriminator VALUE] [view VALUE]
 */
 
 #include "as.h"