Log Message:
libretro-mgba: Update to 0.8.2

0.8.2: (2020-06-14)
Emulation fixes:
 - ARM: Fix timing on Thumb shift instructions
 - GB: Fix GBC game registers after skipping BIOS
 - GB MBC: Support 4MB MBC30 ROMs (fixes mgba.io/i/1713)
 - GB Video: Fix BGPS value after skipping BIOS (fixes mgba.io/i/1717)
 - GBA: Add missing RTC overrides for Legendz games
 - GBA BIOS: Reset renderer when RegisterRamReset called (fixes mgba.io/i/1756)
 - GBA SIO: Fix Multiplayer busy bit
 - GBA SIO: Fix double-unloading active driver
 - GBA Timers: Fix deserializing count-up timers
 - GBA Video: Fix mosaic objects drawing past the end (fixes mgba.io/i/1702)
 - GBA Video: Fix disabling OBJWIN in GL renderer (fixes mgba.io/i/1759)
 - GBA Video: Add missing parts of 256-color mode 0 mosaic (fixes mgba.io/i/1701)
 - GBA Video: Fix double-size OBJ wrapping in GL renderer (fixes mgba.io/i/1712)
 - GBA Video: Simplify sprite cycle counting (fixes mgba.io/i/1279)
 - GBA Video: Fix sprite/backdrop blending regression