ftrace: Simplify the calculation of page number for ftrace_page->records

ftrace: Simplify the calculation of page number for ftrace_page->records

Based on the following two reasones, we could simplify the calculation:

  - If the number after roundup count is not power of 2, we would
    definitely have more than 1 empty page with a higher order.
  - get_count_order() just return current order, so one lower order
    could meet the requirement.

The calculation could be simplified by lower one order level when pages
are not power of 2.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Wei Yang <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>