wl18xx_build: update for ol_r8.a7.02

Update the build script for building wilink8 R8.A2 (ol_r8.a7.02)
version.
Fo the compat_wireless git we are using a slightly different label
(ol_r8.a7.02_34)  to allow building with kernels older then 3.8.

Signed-off-by: Eyal Reizer <eyalr@ti.com>