arm: libgcc: tweak warning from __sync_synchronize

arm: libgcc: tweak warning from __sync_synchronize

My previous patch to add an implementation of __sync_syncrhonize with
a warning trips a testsuite failure in fortran (and possibly other
languages as well) as the framework expects no blank lines in the
output, but this warning was generating one.  So remove the newline
from the end of the message and rely on the one added by the linker
instead.

Since we're there, remove the trailing period from the message as
well, since the convention seems to be not to have one.

libgcc/

	* config/arm/lib1funcs.S (__sync_synchronize): Adjust warning message.