mt76x0: eeprom: fix chan_vs_power map in mt76x0_get_power_info

Report correct eeprom per channel power value.
Fix chan_vs_power map in mt76x0_get_power_info routine

Fixes: f2a2e819 ("mt76x0: remove eeprom dependency from mt76x0_get_power_info")
Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>