libpam: Fix examples build on musl

This came with latest libpam upgrade

../../Linux-PAM-1.5.3/examples/tty_conv.c:9:10: fatal error: 'termio.h' file not found
         ^~~~~~~~~~
1 error generated.

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>