arm64: Fix a broken copyright header in gen_vdso_offsets.sh

I was going to copy this but I didn't want to chase around the build
system stuff so I did it a different way.
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
Link: https://lore.kernel.org/r/20201017002637.503579-1-palmer@dabbelt.comSigned-off-by: Will Deacon <will@kernel.org>

arch/arm64/kernel/vdso/gen_vdso_offsets.sh

@@ -8,7 +8,7 @@
 # Doing this inside the Makefile will break the $(filter-out) function,
 # causing Kbuild to rebuild the vdso-offsets header file every time.
 #
-# Author: Will Deacon <will.deacon@arm.com
+# Author: Will Deacon <will.deacon@arm.com>
 #
 
 LC_ALL=C