i40e: fix build warnings in i40e_alloc.h

Not upstream as it was fixed in a much larger api change in newer
kernels.

gcc-13 rightfully complains that enum is not the same as an int, so fix
up the function prototypes in i40e_alloc.h to be correct, solving a
bunch of build warnings.

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>