batman-adv: avoid skb_linearise() if not needed
batman-adv: avoid skb_linearise() if not needed

Whenever we want to access headers only, we do not need to linearise the whole
packet. Instead we can use pskb_may_pull()

Signed-off-by: Antonio Quartulli <ed91ce0fd2670d4a98b12fc9ec6b7a497c7ed53f@autistici.org>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas