Fix Rosalina menu freeze caused by race condition with GSP/GPU

[RedShyGuy]

The Rosalina menu open/close used svcKernelSetState(0x10000, 2 | 1) to freeze both game threads and GSP simultaneously.
This sometimes caused freezes because GSP could be mid-command when frozen. Any pending GPU completions were never delivered, leaving the game in a deadlocked state on resume, forcing the user to force shut down the system.

Changes (menu.c):

menuEnter: Split the single atomic freeze into a 3-phase sequence:

• freeze game threads first (flag 1) to stop new GPU command submissions
• busy-wait loop (up to 8 iterations) for GPU engines (PSC0, PSC1, Transfer, Cmdlist) to drain, with sleeps between checks to let GSP process its FIFO
• freeze GSP (flag 2) only after GPU is confirmed idle
• on framebuffer allocation failure also now uses the correct sequenced unfreeze

menuLeave:

• unfreeze GSP first with a 2ms delay so it can process any pending hardware interrupts before game threads resume and read the queue