eal: fix type of pointer arithmetic result

eal: fix type of pointer arithmetic result

Adding or subtracting a value to a pointer makes a new pointer
of unknown type.
So typeof() is replaced by (void*) in RTE_PTR_ADD() and RTE_PTR_SUB().

But RTE_PTR_ALIGN_* macros have in their explicit API to return a pointer
of the same type. Since RTE_PTR_ALIGN_CEIL is based on RTE_PTR_ADD, a
typeof() is added to keep the original behaviour.

Signed-off-by: Thomas Monjalon <thomas.monjalon@6wind.com>
Acked-by: Adrien Mazarguil <adrien.mazarguil@6wind.com>