lib/crypto, efi_loader: avoid multiple inclusions of header files

By adding extra symbols, we can now avoid including x509_parser and
pkcs7_parser.h files multiple times.

Suggested-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
Don't include include x509_parser.h twice.
Reviewed-by: Heinrich Schuchardt <xypron.glpk@gmx.de>