games/3dc: Fix crash on boot
The call to XtVaGetValues returns a value that overwrites the bc variable and
smashes the stack. Use a long instead.
PR: 255765
Reported by: grahamperrin@gmail.com
Tested by: rhurling@
MFH: 2021Q2
(cherry picked from commit 339d443d7b97dcef2ad415ff9cf743685ebea304)