microblaze: fix typo in a comment

The double `was' is repeated in a comment. Consequently, remove one
`was' from the comment.
Signed-off-by: Jason Wang <wangborong@cdjrlc.com>
Link: https://lore.kernel.org/r/20211128034823.6930-1-wangborong@cdjrlc.comSigned-off-by: Michal Simek <michal.simek@xilinx.com>

arch/microblaze/kernel/signal.c

@@ -11,7 +11,7 @@
  *
  * 1997-11-28 Modified for POSIX.1b signals by Richard Henderson
  *
- * This file was was derived from the sh version, arch/sh/kernel/signal.c
+ * This file was derived from the sh version, arch/sh/kernel/signal.c
  *
  * This file is subject to the terms and conditions of the GNU General
  * Public License. See the file COPYING in the main directory of this