Specify REGULATORY_GAIN and SX126X_MAX_POWER to prevent exceeding regulatory and hardware limits (i.e. overloading the PA input) respectively.
Also update the build flag to define EBYTE_E22_900M30S instead of just EBYTE_E22, since all the builds on the Discourse topic [New 1W DIY variant: Xiao nRF52840 + Ebyte E22-900M30S](https://meshtastic.discourse.group/t/new-1w-diy-variant-xiao-nrf52840-ebyte-e22-900m30s/7904) are using this module.
That should make it clearer as well that the variant header file should be tweaked if DIY builds are using stronger (E22-900M33S, not commonly available at this time) or weaker (E22-900M22S, not popular for DIY builds due to lack of differentiation from ordinary SX1262 modules).
Retain EBYTE_E22 flag alongside EBYTE_E22_900M30S build flag to prevent possible regressions in code paths generally intended for EBYTE E22 modules.
Signed-off-by: Andrew Yong <me@ndoo.sg>
