clocksource: Remove obsolete ifdef

CONFIG_GENERIC_VDSO_CLOCK_MODE was a transitional config switch which got
removed after all architectures got converted to the new storage model.

But the removal forgot to remove the #ifdef which guards the
vdso_clock_mode sanity check, which effectively disables the sanity check.

Remove it now.

Fixes: f86fd32db7 ("lib/vdso: Cleanup clock mode storage leftovers")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Miklos Szeredi <mszeredi@redhat.com>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20200606221531.845475036@linutronix.de

kernel/time/clocksource.c

@@ -928,14 +928,12 @@ int __clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq)
 
 	clocksource_arch_init(cs);
 
-#ifdef CONFIG_GENERIC_VDSO_CLOCK_MODE
 	if (cs->vdso_clock_mode < 0 ||
 	    cs->vdso_clock_mode >= VDSO_CLOCKMODE_MAX) {
 		pr_warn("clocksource %s registered with invalid VDSO mode %d. Disabling VDSO support.\n",
 			cs->name, cs->vdso_clock_mode);
 		cs->vdso_clock_mode = VDSO_CLOCKMODE_NONE;
 	}
-#endif
 
 	/* Initialize mult/shift and max_idle_ns */
 	__clocksource_update_freq_scale(cs, scale, freq);