boot: zephyr: split esp32 to esp32_devkitc_{wroom,wrover}

This is a follow-up on upstream Zephyr split from `esp32` to distinct
esp32_devkitc_wroom and esp32_devkitc_wrover (see [1] and [2]).

[1] https://github.com/zephyrproject-rtos/zephyr/pull/58454
[2] https://github.com/zephyrproject-rtos/zephyr/commit/3776402f404de76c91142a4487a83dfb37f72bba



Signed-off-by: Marcin Niestroj <m.niestroj@emb.dev>