mwifiex: Reduce endian conversion for REG Host Commands

For multiple REG Host Commands (e.g HostCmd_CMD_802_11_EEPROM_ACCESS,
HostCmd_CMD_MAC_REG_ACCESS etc.) "cpu_to_leX"-converted values are
saved to driver. So, "leX_to_cpu" conversion is required too many
times afterwards in driver.

This patch reduces the endian: conversion without saving "cpu_to_leX"
converted values in driver. This will convert endianness in prepare
command and command response path.

Signed-off-by: Prasun Maiti <prasunmaiti87@gmail.com>
Acked-by: Amitkumar Karwar <akarwar@marvell.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>