lib/vdso: Make __arch_update_vdso_data() logic understandable

lib/vdso: Make __arch_update_vdso_data() logic understandable

commit 9a6b55ac4a44060bcb782baf002859b2a2c63267 upstream.

The function name suggests that this is a boolean checking whether the
architecture asks for an update of the VDSO data, but it works the other
way round. To spare further confusion invert the logic.

Fixes: 44f57d788e7d ("timekeeping: Provide a generic update_vsyscall() implementation")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20200114185946.656652824@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>