scripts: Add Kconfiglib v14.1.0 under scripts directory

We adopt Kconfiglib v14.1.0 sources under scripts directory so that
top-level OpenSBI makefile can directly use Kconfiglib scripts without
expecting users to install a particular version of Kconfiglib on their
build system.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Tested-by: Andrew Jones <ajones@ventanamicro.com>
Acked-by: Atish Patra <atishp@rivosinc.com>
Tested-by: Atish Patra <atishp@rivosinc.com>