qca-ssdk: rework make to allow parallel building

qca-ssdk: rework make to allow parallel building

The current build procedure always wipes away build files, this is
costly as ssdk is a parent dependency on a whole host of packages and
will always end up rebuilding (and in serial) the whole package.

This patch includes:

1. Module Building Optimization: Instead of creating a temporary
directory (temp) and copying files into it for module building,
the directly invoke the module build command with the
necessary paths. This simplifies the build process
and avoids unnecessary file operations, speeding up
the build process and reducing disk usage.

2. Parallel Build Support: By removing the explicit creation of
the temporary directory and associated file copying operations,
and passing in $(MAKE) $(PKG_JOBS) allows building in parallel.

3. Fix `EXTRA_CFLAGS`: This variable is referenced and set within MAKE_FLAGS,
so doesn't preserve spaces. Should have its defined value quoted.

Signed-off-by: Sean Khan <datapronix@protonmail.com>