x86/paravirt: Use common code for paravirt_steal_clock()

x86/paravirt: Use common code for paravirt_steal_clock()

Remove the arch-specific variant of paravirt_steal_clock() and use
the common one instead.

With all archs supporting Xen now having been switched to the common
variant, including paravirt.h can be dropped from drivers/xen/time.c.

Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20260105110520.21356-12-jgross@suse.com