gcc: fix HOST_GCC_COMMON_WRAPPER_TARGET_FLOAT_ABI typos

gcc: fix HOST_GCC_COMMON_WRAPPER_TARGET_FLOAT_ABI typos

The HOST_GCC_COMMON_WRAPPER_TARGET_FLOAT_ABI variable was incorrectly
used as HOST_GCC_COMMON_WRAPPER_TARGET_FLOATABI_, which would always
be empty.

In practice, this block of code is only used on Blackfin (which has
BR2_GCC_ARCH_HAS_CONFIGURABLE_DEFAULTS unset) and Blackfin doesn't use
float-abi, so this block of code is in fact useless. But even if it's
useless, it's better to have it without typos.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>