arm_disassembler: bugfix, MRRC instruction not recognized

arm_disassembler: bugfix, MRRC instruction not recognized

A copy-and-paste error in the arm_disassembler opcode evaluation
disabled the recognition of MRRC instructions.
According to the arm architecture ref. manual issue E or later, MRRC and MCRR
instructions are identified by opcode bits 20-27: MCRR = 0xc4, MRRC = 0xc5.
Error found by static code analysis using a semantic pattern to
detect duplicated tests xand.cocci, see coccinellery.org

Change-Id: Ic41426edb51c6816e11dc3d35ef9382ab34af486
Signed-off-by: Alexander Kurz <akurz@blala.de>
Reviewed-on: http://openocd.zylin.com/3363
Reviewed-by: Uwe Bonnes <bon@elektron.ikp.physik.tu-darmstadt.de>
Tested-by: jenkins
Reviewed-by: Andreas Fritiofson <andreas.fritiofson@gmail.com>