Silence ARM as error "MOV Rd, Rs" two low regs with clang/armv5/thumb1

Clang -target armv5te-none-linux-androideabi -mthumb generates
"MOV Rd, Rs" with two low regs and expect it doesn't change CPSR.
The only encoding in thumb1 allows it is "Hi register operations"
with H1=0 && H2=0 but the behavior is undefined in v5t until v6.
The assembler from binutils-2.22 (compiled with gcc4.7) starts to
check and abort with message reads:

  main.s:86: Error: MOV Rd, Rs with two low registers is not permitted on this architecture -- mov r0,r4

Temporily disable this error before clang is fixed.

Change-Id: I3332707e28c00af220896c64b98deef1a4237749

Author: Andrew Hsieh <andrewhsieh@google.com>
Date:   Thu Apr 18 13:47:12 2013 +0800