EmbeddedPkg: list module-internal header files in INF [Sources]

EmbeddedPkg: list module-internal header files in INF [Sources]

The BaseTools build feature introduced for TianoCore#1804 / in commit
1fa6699e6cd4 ("BaseTools: Add a checking for Sources section in INF file",
2019-06-10) logs some (non-fatal) warnings about unlisted internal header
files. List those files explicitly.

Note: header files are added in lexicographical order only if the
underlying INF file already keeps the [Sources] and [LibraryClasses]
sections in lexicographical order. Otherwise, header files are added in
rough "logical" order.

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Leif Lindholm <leif.lindholm@linaro.org>
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Philippe Mathieu-Daude <philmd@redhat.com>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>