x86/mm/cpa: Split, rename and clean up try_preserve_large_page()

x86/mm/cpa: Split, rename and clean up try_preserve_large_page()

Avoid the extra variable and gotos by splitting the function into the
actual algorithm and a callable function which contains the lock
protection.

Rename it to should_split_large_page() while at it so the return values make
actually sense.

Clean up the code flow, comments and general whitespace damage while at it. No
functional change.

Signed-off-by: Thomas Gleixner <[email protected]>
Reviewed-by: Dave Hansen <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Bin Yang <[email protected]>
Cc: Mark Gross <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]