sys/boot/geli build warning fixes

[aprieger_llnw.com]

Summary

Code changes to fix warnings during build time of the application in the sys/boot/gelit folder

Test Plan

I have tested the fix on all architextures and targets, using the "make TARGET=XXX TARGET_ARCH=YYY" and the warnings have all been removed

[aprieger_llnw.com]

Changelog:
Pre-fix warnings located at: https://gist.github.com/aprieger-llnw/cb7e4248bc235c1d24a3e82fb30998d5

1. sys/boot/geli/geliboot_crypto.c
   • warning: incompatible pointer types passing 'struct aes_xts_ctx *' to parameter of type 'caddr_t' (aka 'char *') [-Wincompatible-pointer-types]
     • fix: explicitly casted the parameters to type caddr_t on lines 85, 90, 95