Fix Libretro-MAME "offscreenreload" light gun option

[TrickoUK]

Disclosure, the fix was found using Claude code.

Light guns work fine in Libretro-MAME as long as the "offscreen reload" option is turned off.
If it's turned on however the game will fail to launch with this error -

[libretro INFO] Game description: The House of the Dead (Revision A)
[INFO] [Environ] SET_ROTATION: "0" (0 deg).
[libretro ERROR] Error: unknown option: -offscreen_reload
[ERROR] [Content] Failed to load content.

As that option has been removed from standalone, and Libretro MAME now.
Instead the offscreen reload is loaded as a helper plugin now, which was already done for standalone MAME in it's generator, so fix is just to apply the same here.

I kept the more conservative fix to only apply it if its MAME system specifically given Claudes comment about the other systems also potentially picking up from this generator as I don't have any of them to test with to be sure if they need this or not.

Tested in a custom build of Batocera v44 source on x86 build with Sinden light gun, offscreen button now working fine in addition to actual shooting off screen still.

[dmanlfc]

looks ok, remove all the extra comment though please

[TrickoUK]

Done.

Just for future reference, I've got some more light gun related fixes for other retroarch systems working, and I've also bumped the emulator and exposed more options into the ES advanced menu for options that were missing.

Is one PR per system OK, or are multiple focused PRs per topic, ie bump emu/gun fix/add options better?
Just looking to best fit in with how people like to review things in general.

[Tovarichtch]

Done.

Just for future reference, I've got some more light gun related fixes for other retroarch systems working, and I've also bumped the emulator and exposed more options into the ES advanced menu for options that were missing.

Is one PR per system OK, or are multiple focused PRs per topic, ie bump emu/gun fix/add options better? Just looking to best fit in with how people like to review things in general.

It is OK yes. But tag me for anything light gun related stuff.