Fix VFS stat command

[garbear]

Description

Fixes bug in the VFS wrapper causing UAE to not find BIOS files.

Motivation and context:

Reported here: https://forum.kodi.tv/showthread.php?tid=384979

[Copilot]

Pull request overview

Fixes a VFS wrapper bug where file/stat flag bitmasks were being combined with &= instead of |=, causing required flags to never be set (which can prevent UAE from detecting BIOS files via stat/validity checks).

Changes:

• Use |= (bitwise OR) to accumulate Kodi VFS open flags for read-only file opens.
• Use |= (bitwise OR) to accumulate retro_vfs stat result bitmask flags (IS_VALID, IS_DIRECTORY, IS_CHARACTER_SPECIAL).

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[Copilot]

Pull request overview

This PR fixes incorrect bitmask manipulation in the libretro VFS wrapper so that file open flags and stat() result flags are set correctly, addressing UAE failing to locate BIOS files.

Changes:

• Fix OpenFile() to set Kodi VFS read flags with bitwise OR (|=) instead of AND (&=).
• Fix Stat() to set RETRO_VFS_STAT_* result flags with bitwise OR (|=) instead of AND (&=).

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[garbear]

Reported working in the forum: https://forum.kodi.tv/showthread.php?tid=384979