bfin: allow ".=.+delta"

[Jeff Law]

On Fri, 2020-04-17 at 12:47 +0930, Alan Modra via Binutils wrote:
> BFIN has lots of instructions that contain "=", so "sym = expression"
> is disabled for that target.  This makes an exception for assignment
> to dot, fixing the recent regression of ld-scripts/pr18963.
> 
> 	* config/tc-bfin.h (TC_EQUAL_IN_INSN): Allow assignment to dot.
THanks.  My tester tripped over that yesterday.  bfin was the only port affected.

jeff
>