[Suggestion] Keyboard auto-detect

Raspberry Pi 4 B 4gb
Lakka OS Nightly RPI 4 arm Apr 15 2021

Hardware: USB Keyboard and USB Mouse
Cores: DosBox and DosBox-SVN

Im not sure if it is a bug, but when I started a first time setup and attempt at DOSBox the keyboard was not allowing me to input certain keys. IE P was pausing, I quickly had to delete all the keyboard hotkeys, then when Enter and some other keys such as the arrows and x was not inputting I went to controls to change them from gamepad to keyboard and mouse for the core.

It still did not allow me to use those keys until I disconnected the gamepad so RA will not get confused, then using the Keyboard I had to change it from gamepad to keyboard+ mouse and then delete the keys form the input list.

I went ahead and then tested it out on RetroArch (1.9.1) that was installed on my Linux Mint 20.1 Desktop PC. I never had DosBox on it so I downloaded the core and saw that it was doing the same thing there.

Reproduce the behavior on RetroArch 1.9.1 with the DosBox or DosBox-SVN core, using a USB keyboard, USB mouse, and gamepad on the reported Linux systems. Compare keyboard input with and without gamepad bindings; done should mean keys such as P, Enter, arrows, and X work without deleting mappings or disconnecting the gamepad.