usertools: show valid hugepage sizes if wrong request

usertools: show valid hugepage sizes if wrong request

If user requests a hugepage size which is not supported by the system,
currently user gets an error message saying that the requested size
is not a valid system huge page size. In addition to this if we display
the valid hugepage sizes it will be convenient for the user to request
the right size next time.

Signed-off-by: Sarosh Arif <sarosh.arif@emumba.com>
Acked-by: Stephen Hemminger <stephen@networkplumber.org>