doc: uefi: add HTTP Boot support

This adds the description about HTTP Boot.

[Ilias add the new EFI_HTTP_BOOT option in docs]
Lore: https://lore.kernel.org/u-boot/20231110042542.3797301-1-masahisa.kojima@linaro.org/T/#m36acf922a888cc14f74e823ec57bacd9f977194e


Signed-off-by: Masahisa Kojima <masahisa.kojima@linaro.org>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>