board/qualcomm: introduce phone config

board/qualcomm: introduce phone config

Phones don't have keyboards! Introduce a phone-specific config fragment
and associated environment file to make U-Boot more useful on these
devices. This allows for navigating via the buttons and enabling
various USB gadget modes or displaying info about U-Boot.

Reviewed-by: Simon Glass <sjg@chromium.org>
Tested-by: Danila Tikhonov <danila@jiaxyga.com> # google-sunfish
Tested-by: Jens Reidel <adrian@mainlining.org> # xiaomi-davinci
Link: https://lore.kernel.org/r/20250331-qcom-phones-v4-1-f52e57d3b8c6@linaro.org
Signed-off-by: Caleb Connolly <caleb.connolly@linaro.org>