sched/vtime: Do not include <asm/vtime.h> header

There is no architecture-specific code or data left
that generic <linux/vtime.h> needs to know about.
Thus, avoid the inclusion of <asm/vtime.h> header.

Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Nicholas Piggin <npiggin@gmail.com>
Link: https://lore.kernel.org/r/f7cd245668b9ae61a55184871aec494ec9199c4a.1712760275.git.agordeev@linux.ibm.com