if_iwm - Add firmware API definitions for TX power commands.

• While there remove unused IWM_UCODE_TLV_CAPA_LMAC_UPLOAD definition,

which isn't defined in iwlwifi.

Taken-From: Linux iwlwifi

Submitted by: Augustin Cavalier <waddlesplash@gmail.com> (Haiku)
Obtained from: DragonFlyBSD (fd4f9de8bc72ea961e50829b45b59d0549040b7d)