toolchain: bump ARC tools to arc-2016.03-rc2

toolchain: bump ARC tools to arc-2016.03-rc2

This change switches ARC tools to RC2 of the most recent arc-2016.03
version.

Essentially once final release is ready version will be bumped again.

ARC GNU tools of version arc-2016.03 bring some quite significant
changes like:
 * Binutils v2.26+ (upstream commit id 202ac19 with additional ARC patches)
 * GCC v4.8.5
 * GDB 7.10

More about changes, improvements and fixes could be found here:
https://github.com/foss-for-synopsys-dwc-arc-processors/toolchain/releases/tag/arc-2016.03-rc2

Also in this change we realign custom Buildroot patches for binutils and
gcc for ARC tools. Looks like earlier most of arch-independent patches
for binutils and gcc were either unintentionally removed or not even
added in patch folders for ARC's binutils and gcc. Now arch-independent
patches for binutils-2.26 and gcc-4.8.5 were added in
package/{binutils|gcc}/arc-2016.03-rc2 folders.

Build and run-tested in nSIM for both ARC700 and ARC HS38.

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>