arm: fix compile in thumb mode
arm: fix compile in thumb mode

Fix a regression introduced by commit
0550ecce0e6580c5ad34e9a9a39ff18ccf8774f9

Reported by Buildroot developers.

Embedded test must be extented to ARMv7 thumb2 builds to
find such regressions next time. It wasn't triggered by a
cortex-m4 ARM noMMU build.

kraj/uclibc-ng,brgl/uclibc-ng,brgl/uclibc-ng,brgl/uclibc-ng,wbx-github/uclibc-ng,brgl/uclibc-ng,wbx-github/uclibc-ng,kraj/uclibc-ng,kraj/uclibc-ng,foss-for-synopsys-dwc-arc-processors/uClibc,wbx-github/uclibc-ng,foss-for-synopsys-dwc-arc-processors/uClibc,foss-for-synopsys-dwc-arc-processors/uClibc,foss-for-synopsys-dwc-arc-processors/uClibc,kraj/uclibc-ng,wbx-github/uclibc-ng