[GAS][ARM]Use frag's thumb_mode information when available.

[Nicholas Clifton]

Hi Renlin,

> 2015-06-02  Renlin Li  <renlin.li@arm.com>
>          * config/tc-arm.c (arm_init_frag): Use frag's thumb_mode
>          information when available.

Approved - please apply.

Cheers
   Nick