Fixed several issues with SO_EL_SYMPATHY

- Corrected an issue that caused the elemental's HP and SP would
  _decrease to_ summon_level*5% instead of _increasing by_ said amount.
- Corrected an issue that decreased the SP cost of summon elemental
  skills by 5% even when the Spirit Sympathy skill wasn't present.
- Added/renamed some variables to prevent confusion. Please don't reuse
  'i' variables for things that aren't array indices. Or don't reuse
  variables altogether for different purposes than their original one.
- Special thanks to Kisuka.

Signed-off-by: Haru <haru@dotalux.com>