wifi: brcmsmac: phy: Remove unreachable error handling code

wlc_phy_txpwr_srom_read_lcnphy() in wlc_phy_attach_lcnphy() always
returns true, making the error handling code unreachable. Change the
function's return type to void and remove the dead code, similar to
the cleanup done for wlc_phy_txpwr_srom_read_nphy() in commit
47f0e32ffe4e ("wifi: brcmsmac: phy: Remove unreachable code").

Signed-off-by: Ingyu Jang <ingyujang25@korea.ac.kr>
Acked-by: Arend van Spriel <arend.vanspriel@broadcom.com>
Link: https://patch.msgid.link/20260131172355.3367673-1-ingyujang25@korea.ac.kr
Signed-off-by: Johannes Berg <johannes.berg@intel.com>