sparc64: vdso: Replace code patching with runtime conditional

sparc64: vdso: Replace code patching with runtime conditional

The patching logic is unnecessarily complicated and stands in the way of
the adoption of the generic vDSO framework.

Replace it by a simple runtime switch, similar to other architectures.

Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Tested-by: Andreas Larsson <andreas@gaisler.com>
Reviewed-by: Andreas Larsson <andreas@gaisler.com>
Acked-by: Andreas Larsson <andreas@gaisler.com>
Link: https://lore.kernel.org/lkml/87ecu9tfhw.ffs@tglx/
Link: https://patch.msgid.link/20260304-vdso-sparc64-generic-2-v6-6-d8eb3b0e1410@linutronix.de