clocksource/drivers/hyper-v: Re-enable VDSO_CLOCKMODE_HVCLOCK on X86

Mohammed reports (https://bugzilla.kernel.org/show_bug.cgi?id=213029)
the commit e4ab4658f1cf ("clocksource/drivers/hyper-v: Handle vDSO
differences inline") broke vDSO on x86. The problem appears to be that
VDSO_CLOCKMODE_HVCLOCK is an enum value in 'enum vdso_clock_mode' and
'#ifdef VDSO_CLOCKMODE_HVCLOCK' branch evaluates to false (it is not
a define).

Use a dedicated HAVE_VDSO_CLOCKMODE_HVCLOCK define instead.

Fixes: e4ab4658f1cf ("clocksource/drivers/hyper-v: Handle vDSO differences inline")
Reported-by: Mohammed Gamal <[e-mail]>
Suggested-by: Thomas Gleixner <[e-mail]>
Signed-off-by: Vitaly Kuznetsov <[e-mail]>
Signed-off-by: Thomas Gleixner <[e-mail]>
Reviewed-by: Michael Kelley <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

arch/x86/include/asm/vdso/clocksource.h

···
 	VDSO_CLOCKMODE_PVCLOCK,	\
 	VDSO_CLOCKMODE_HVCLOCK
 
+#define HAVE_VDSO_CLOCKMODE_HVCLOCK
+
 #endif /* __ASM_VDSO_CLOCKSOURCE_H */

drivers/clocksource/hyperv_timer.c

···
 	hv_set_register(HV_REGISTER_REFERENCE_TSC, tsc_msr);
 }
 
-#ifdef VDSO_CLOCKMODE_HVCLOCK
+#ifdef HAVE_VDSO_CLOCKMODE_HVCLOCK
 static int hv_cs_enable(struct clocksource *cs)
 {
 	vclocks_set_used(VDSO_CLOCKMODE_HVCLOCK);
···
 	.flags	= CLOCK_SOURCE_IS_CONTINUOUS,
 	.suspend= suspend_hv_clock_tsc,
 	.resume	= resume_hv_clock_tsc,
-#ifdef VDSO_CLOCKMODE_HVCLOCK
+#ifdef HAVE_VDSO_CLOCKMODE_HVCLOCK
 	.enable = hv_cs_enable,
 	.vdso_clock_mode = VDSO_CLOCKMODE_HVCLOCK,
 #else