package/binutils: remove special case version selection for ARM Thumb

package/binutils: remove special case version selection for ARM Thumb

Binutils 2.29 and 2.30 are affected by a bug in ADR and ADRL
pseudo-instruction [1] that was fixed in Binutils 2.31 [2].

  * The ADR and ADRL pseudo-instructions supported by the ARM assembler
    now only set the bottom bit of the address of thumb function symbols
    if the -mthumb-interwork command line option is active.

Due to this issue, we were default to binutils 2.28 for ARM Thumb. But
now that the issue has been fixed in binutils 2.31 and that this
version is the default, the special casing to use 2.28 is no longer
needed.

[1] https://sourceware.org/bugzilla/show_bug.cgi?id=21458
[2] https://sourceware.org/ml/binutils/2018-07/msg00213.html

Signed-off-by: Romain Naour <romain.naour@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>