rsi: move common part of firmware load to separate function

Till software bootloader ready state, communication with device is common
for 9113 and 9116. Hence moved that part of firmware loading to separate
function rsi_prepare_fw_load(). Also LMAC_VER_OFFSET is different for 9113
and 9116, so renamed existing macro to LMAC_VER_OFFSET_9113

Signed-off-by: Siva Rebbagondla <siva8118@gmail.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>