u-boot-pinebook: Fixes options handling and Python tool handling

- PKG_DEFAULT_OPTIONS should not be used in package Makefile-s,
  use PKG_SUGGESTED_OPTIONS instead.
- u-boot.mk already defines that Python is needed, no need to redefine it there.

Thanks to <martin> for reporting these problem on tech-pkg@!

Index: Makefile
===================================================================
RCS file: /cvsroot/pkgsrc/sysutils/u-boot-pinebook/Makefile,v
retrieving revision 1.8
diff -u -p -r1.8 Makefile
--- Makefile	8 Nov 2018 19:41:30 -0000	1.8
+++ Makefile	9 Nov 2018 11:31:47 -0000
@@ -15,17 +15,13 @@ EXTRACT_SUFX=		.tar.gz
 DISTINFO_FILE=		${.CURDIR}/../../sysutils/u-boot-pinebook/distinfo
 PATCHDIR=		${.CURDIR}/../../sysutils/u-boot-pinebook/patches
 
-# Switch to EL1 before booting kernel (required for 32-bit support)
-PKG_DEFAULT_OPTIONS+=	el1
-
 post-extract:
 	${CP} ${PREFIX}/share/arm-trusted-firmware/sun50iw1p1/bl31.bin ${WRKSRC}
 
 post-build:
 	${CAT} ${WRKSRC}/spl/sunxi-spl.bin ${WRKSRC}/u-boot.itb > ${WRKSRC}/u-boot-sunxi-with-spl.bin
 
-PYTHON_FOR_BUILD_ONLY=	yes
-.include "../../lang/python/tool.mk"
-
 .include "../../sysutils/arm-trusted-firmware-sun50iw1p1/buildlink3.mk"
 .include "../../sysutils/u-boot/u-boot-arm64.mk"
+# Switch to EL1 before booting kernel (required for 32-bit support)
+PKG_SUGGESTED_OPTIONS+=	el1