bcmdhd: Enable Ad-Hoc (IBSS) mode
backported from tuna
see https://github.com/CyanogenMod/android_kernel_samsung_tuna/commit/4da33984c1c6e07a278f2e26687472e1a67bb777
bcmdhd: restored ARP offload agent mode
taken from tuna
https://github.com/CyanogenMod/android_kernel_samsung_tuna/commit/6ccf1c0af64307805324b58142a2664043db277c