wolfssl: Adjust version for apk

wolfssl: Adjust version for apk

Adjust wolfssl version for apk by removing the "-stable"
from the OpenWrt version, although it is still needed for
upstream download archive name.

Define PKG_BUILD_DIR accordingly.

Utilize new short version to simplify ABI_VERSION calculation.

Signed-off-by: Hannu Nyman <hannu.nyman@iki.fi>
Link: https://github.com/openwrt/openwrt/pull/16906
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
(cherry picked from commit be952e98bc1d768a0da5b84e59a6e7c04a1cdab8)