m68k: Fix ndelay() macro

The current ndelay() macro definition has an extra semi-colon at the
end of the line thus leading to a compilation error when ndelay is used
in a conditional block without curly braces like this one:

	if (cond)
		ndelay(t);
	else
		...

which, after the preprocessor pass gives:

	if (cond)
		m68k_ndelay(t);;
	else
		...

thus leading to the following gcc error:

	error: 'else' without a previous 'if'

Remove this extra semi-colon.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Fixes: c8ee038b ("m68k: Implement ndelay() based on the existing udelay() logic")
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>