recipes: Drop remaining PR values from recipes

* as oe-core did in:
  https://git.openembedded.org/openembedded-core/commit/?id=d4c346e8ab

* when people are have to maintain own PRs for recipes in oe-core, they
  might add them for meta-oe recipes at the same time when upgrading
  to next LTS

Signed-off-by: Martin Jansa <martin.jansa@gmail.com>
Signed-off-by: Khem Raj <raj.khem@gmail.com>

meta-oe/recipes-benchmark/lmbench/lmbench_3.0-a9.bb

@@ -10,7 +10,6 @@ inherit autotools-brokensep update-alternatives
 DEPENDS += "libtirpc"
 CFLAGS += "-I${STAGING_INCDIR}/tirpc"
 
-PR = "r2"
 
 SRC_URI = "${SOURCEFORGE_MIRROR}/lmbench/lmbench-${PV}.tgz \
            file://lmbench-run \

meta-oe/recipes-benchmark/tiobench/tiobench_0.3.3.bb

@@ -3,7 +3,6 @@ HOMEPAGE = "http://sourceforge.net/projects/tiobench/"
 LICENSE = "GPL-2.0-only"
 LIC_FILES_CHKSUM = "file://COPYING;md5=c93c0550bd3173f4504b2cbd8991e50b"
 
-PR = "r1"
 
 SRC_URI = "\
     http://sourceforge.net/projects/tiobench/files/tiobench/${PV}/${BP}.tar.gz \