Changes since v1.0:

Added 896x504 and 480x272 video modes

Added 30FPS support

VitaShell's USB mode should work (starting at VitaShell 1.95) but a reboot will be needed after disabling USB in order to get this plugin working again

List of supported video modes:

960x544 @ 30 FPS and (less than) 60 FPS

896x504 @ 30 FPS and (about) 60 FPS

480x272 @ 30 FPS and 60 FPS

Fixed 480x272 support thanks to u/Kaizu_vita

Removed unused interrupt endpoint, which seems that allocated USB bandwidth that could not be used for sending the video data. Before this change, sending a 960x544 NV12 frame took ~16ms, now that this endpoint is removed and more bandwidth is available, sending a frame takes ~13ms.
Colorspace conversion takes ~2.5ms, therefore now it takes 13+2.5 = 15.5ms, so 60FPS can be achieved at full resolution!
Minor cleanups
Compiling with -O2
Files:

udcd_uvc.skprx: doesn't turn the display on/off
udcd_uvc_oled_off.skprx: turns the display on/off on OLED Vitas (Vita 1000)
udcd_uvc_lcd_off.skprx: turns the display on/off on LCD Vitas (Vita 2000)

Add frame descriptor for 1280x720 (with the Sharpscale plugin, the Vita is able to submit 1280x720
framebuffers to the kernel)
Dynamically allocate memory for UVC frame: allocates only as much memory as needed and only
when needed, otherwise with a 1280x720 buffer for the UVC frame, the kernel frequently runs out
of memory.
Minor code fixes