[][openwrt][common][Fix build error in openssl-fips-ext]

[Description]
Remove Build/Prepare in Makefile.
Make it use default Build/Prepare.

[Release-log]

Change-Id: I5cfa60558c0f9e06779047776f17b4e74b45a5b5
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/8267477
2 files changed