meta: enable parallel build for several recipes

I used a for loop to build these packages more than 520 times, these
recipes never failed.

(From OE-Core rev: 7957c5bc2771a763d26e50e716733c6335cef3c2)

Signed-off-by: Robert Yang <liezhi.yang@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-devtools/autoconf/autoconf_2.69.bb

@@ -2,8 +2,6 @@ require autoconf.inc
 
 PR = "r11"
 
-PARALLEL_MAKE = ""
-
 LICENSE = "GPLv2 & GPLv3"
 LIC_FILES_CHKSUM = "file://COPYING;md5=751419260aa954499f7abaabaa882bbe \
 		    file://COPYINGv3;md5=d32239bcb673463ab874e80d47fae504"

meta/recipes-devtools/dpkg/dpkg.inc

@@ -11,8 +11,6 @@ RDEPENDS_${PN}_class-native = "xz-native"
 
 S = "${WORKDIR}/${BPN}-${PV}"
 
-PARALLEL_MAKE = ""
-
 inherit autotools gettext perlnative pkgconfig systemd
 
 python () {

meta/recipes-devtools/json-c/json-c_0.12.bb

@@ -11,8 +11,6 @@ SRC_URI[sha256sum] = "000c01b2b3f82dcb4261751eb71f1b084404fb7d6a282f06074d3c1707
 
 RPROVIDES_${PN} = "libjson"
 
-PARALLEL_MAKE = ""
-
 inherit autotools
 
 do_configure_prepend() {

meta/recipes-devtools/mtd/mtd-utils_git.bb

@@ -29,6 +29,4 @@ FILES_mtd-utils-jffs2 = "${sbindir}/mkfs.jffs2 ${sbindir}/jffs2dump ${sbindir}/j
 FILES_mtd-utils-ubifs = "${sbindir}/mkfs.ubifs ${sbindir}/ubi*"
 FILES_mtd-utils-misc = "${sbindir}/nftl* ${sbindir}/ftl* ${sbindir}/rfd* ${sbindir}/doc* ${sbindir}/serve_image ${sbindir}/recv_image"
 
-PARALLEL_MAKE = ""
-
 BBCLASSEXTEND = "native"

meta/recipes-devtools/python/python-pygobject_2.28.3.bb

@@ -18,8 +18,6 @@ S = "${WORKDIR}/pygobject-${PV}"
 
 EXTRA_OECONF += "--disable-introspection"
 
-PARALLEL_MAKEINST = ""
-
 inherit autotools distutils-base pkgconfig
 
 # necessary to let the call for python-config succeed

meta/recipes-devtools/valgrind/valgrind_3.10.1.bb

@@ -36,7 +36,6 @@ inherit autotools ptest
 EXTRA_OECONF = "--enable-tls --without-mpicc"
 EXTRA_OECONF_armv7a = "--enable-tls -host=armv7-none-linux-gnueabi --without-mpicc"
 EXTRA_OEMAKE = "-w"
-PARALLEL_MAKE = ""
 
 do_install_append () {
     install -m 644 ${B}/default.supp ${D}/${libdir}/valgrind/