[ARM] Factor out the thumb1 -Os implementation.

[ARM] Factor out the thumb1 -Os implementation.

The patch moves the inline ASM thumb1 -O2 implementation out into its
own .S file.

Tested by building newlib and comparing libc.a binaries before and
after for all permutations of:

      Architectures:
        armv4 armv4t armv5 armv5t armv5te armv6 armv6j armv6k
        armv6z armv6kz armv6t2 armv6-m armv6s-m armv7 armv7-a
        armv7ve armv7-r armv7-m armv7e-m armv8-a iwmmxt iwmmxt2

      ISAs:
        thumb arm

      Optimization Levels:
        Os O2

      Excluding:
        armv6s-m -mthumb
        armv6-m -mthumb

        armv6zk -mthumb
        armv6z -mthumb
        armv6k -mthumb
        armv6j -mthumb