timekeeping: Remove CONFIG_GENERIC_TIME_VSYSCALL_OLD

timekeeping: Remove CONFIG_GENERIC_TIME_VSYSCALL_OLD

As of d4d1fc61eb38f (ia64: Update fsyscall gettime to use modern
vsyscall_update)the last user of CONFIG_GENERIC_TIME_VSYSCALL_OLD
have been updated, the legacy support for old-style vsyscall
implementations can be removed from the timekeeping code.

(Thanks again to Tony Luck for helping remove the last user!)

[jstultz: Commit message rework]

Signed-off-by: Miroslav Lichvar <[email protected]>
Signed-off-by: John Stultz <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Cc: Prarit Bhargava <[email protected]>
Cc: Tony Luck <[email protected]>
Cc: Richard Cochran <[email protected]>
Cc: Stephen Boyd <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]