ARC: Update Linux samples

There's no point in keeping samples which are in its essense
just a sub-set of multilib toolchain.

But still we'd like to cover quite unusual but really existing
case - ARC750, i.e. ARC700 with MMU but without so-called
atomic instructions (LLOCK/SCOND). To support this HW variation
we need:
 1) Compile all target binaries without "-matomics" or even
    better "-mno-atomics" so that's even future-proof
    (as we may decide to enable "-matomics" by default for Linux
     targets which is a recommented setup).
 2) Configure libc such that it uses Linux-kernel-assisted implementation
    of atomic operation via "arc_usr_cmpxchg" syscall,
    see https://cgit.uclibc-ng.org/cgi/cgit/uclibc-ng.git/commit/?id=b985fa069187e4c5a7ee84213d9fbead2f219ce5

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>

samples/arc-arc700-linux-uclibc/crosstool.config

@@ -1,6 +1,6 @@
 CT_ARCH_ARC=y
 CT_TARGET_ALIAS="arc-linux"
-CT_TARGET_CFLAGS="-matomic"
+CT_TARGET_CFLAGS="-mno-atomic"
 CT_TARGET_VENDOR="snps"
 CT_KERNEL_LINUX=y
 CT_LIBC_UCLIBC=y

samples/arc-arc700-linux-uclibc/reported.by

@@ -1,3 +1,3 @@
 reporter_name="Alexey Brodkin"
 reporter_url="http://embarc.org"
-reporter_comment="ARCompact default Linux toolchain"
+reporter_comment="ARCompact uClibc Linux toolchain without atomics"

samples/arc-archs-linux-uclibc/crosstool.config

@@ -1,7 +0,0 @@
-CT_ARCH_ARC=y
-CT_TARGET_ALIAS="arc-linux"
-CT_TARGET_CFLAGS="-matomic"
-CT_TARGET_VENDOR="snps"
-CT_KERNEL_LINUX=y
-CT_LIBC_UCLIBC=y
-CT_ARCH_CPU="hs38"

samples/arc-archs-linux-uclibc/reported.by

@@ -1,3 +0,0 @@
-reporter_name="Alexey Brodkin"
-reporter_url="http://embarc.org"
-reporter_comment="ARCv2 default Linux toolchain"