feature-arm-thumb.inc: Fix ARMPKGSFX_THUMB value

* my previous thumb related commit:
  commit 3e760031f91fb87c3e2f62b77a117eb41164f259
  Author: Martin Jansa <martin.jansa@gmail.com>
  Date:   Wed Feb 18 15:40:35 2015 +0100

    feature-arm-thumb.inc: respect ARM_INSTRUCTION_SET when adding thumb
    suffix

  unfortunately removed conditional on "thumb" in TUNE_FEATURES, when
  setting ARMPKGSFX_THUMB

* in case we have MACHINE without "thumb" in TUNE_FEATURES and distro
  setting ARM_INSTRUCTION_SET to "thumb" we end with:
  ARM_INSTRUCTION_SET="thumb"
  ARM_THUMB_OPT="thumb"
  ARM_M_OPT="thumb"

  # TUNE_CCARGS correctly not adding -mthumb
  TUNE_CCARGS=" -march=armv7-a  -mthumb-interwork -mfloat-abi=softfp -mfpu=neon"

  # but ARMPKGSFX_THUMB and TUNE_PKGARCH including "t2":
  ARMPKGSFX_THUMB="t2"
  TUNE_PKGARCH="armv7at2-vfp-neon"

  # causing following error:
  Error, the PACKAGE_ARCHS variable does not contain TUNE_PKGARCH (armv7at2-vfp-neon).

(From OE-Core rev: 951200673af27538beaef647a33308b4f15d1fb0)

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/conf/machine/include/arm/feature-arm-thumb.inc

@@ -33,7 +33,7 @@ TUNE_CCARGS .= "${@bb.utils.contains('TUNE_FEATURES', 'thumb', ' -m${ARM_M_OPT}'
 OVERRIDES .= "${@bb.utils.contains('TUNE_FEATURES', 'thumb', ':thumb', '', d)}"
 
 # Add suffix from ARM_THUMB_SUFFIX only if after all this we still set ARM_M_OPT to thumb
-ARMPKGSFX_THUMB .= "${@ d.getVar('ARM_THUMB_SUFFIX', True) if d.getVar('ARM_M_OPT', True) == 'thumb' else ''}"
+ARMPKGSFX_THUMB .= "${@bb.utils.contains('TUNE_FEATURES', 'thumb', '${ARM_THUMB_SUFFIX}', '', d) if d.getVar('ARM_M_OPT', True) == 'thumb' else ''}"
 
 # Whether to compile with code to allow interworking between the two
 # instruction sets. This allows thumb code to be executed on a primarily