libkmod: Introduce elf_range_valid

libkmod: Introduce elf_range_valid

The range check should be performed in its own function for better
readability and reusability. Also, perform range checks before loops
or otherwise repeated calls by checking whole ranges instead of
single byte areas within said ranges iteratively.

Signed-off-by: Tobias Stoeckmann <tobias@stoeckmann.org>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
Link: https://github.com/kmod-project/kmod/pull/196
Signed-off-by: Lucas De Marchi <lucas.de.marchi@gmail.com>