populate_sdk_rpm: Only remove trailing whitespace, not all whitespace

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
libnewt-python: Don't write a whiptail package

The whiptail package is written by the libnewt recipe so for the python version
we need to ensure its not in PACKAGES.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>