libkmod: Properly skip first symbol entry

libkmod: Properly skip first symbol entry

This fixes a regression introduced while converting pointer to
offset arithmetics.

The for-loop itself starts at 1 already, so reflect this with the
manually performed offset + length calculation right at the start.

Closes: https://github.com/kmod-project/kmod/issues/214
Fixes: 25ab561b ("libkmod: Use ELF offsets more often")
Reported-by: Emil Velikov <emil.l.velikov@gmail.com>
Signed-off-by: Tobias Stoeckmann <tobias@stoeckmann.org>
Link: https://github.com/kmod-project/kmod/pull/215
Signed-off-by: Lucas De Marchi <lucas.de.marchi@gmail.com>