arch-armv4.inc, arch-armv5.inc: Do not tie generating thumb ISA to -march

arch-armv4.inc, arch-armv5.inc: Do not tie generating thumb ISA to -march

-march=armv5't'e means that CPU can execute thumb ISA, we do not need to
tie this to exclusively generating thumb ISA, this change means that
when we have thumb in tune features then it can use 't' in -march
options irrespective of ISA being thumb or arm.

This fixes derivative of armv5 tunes and paves way for gcc9 where e.g.
armv5e is dropped and minimum arch supported is armv5te

(From OE-Core rev: 49bc3eab2897307a92b538a045e3d4dce245b0e0)

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>