scripts: introduce float type as a string

With the upcoming softfp support, the case..esac test would become
a bit convoluted if it were to test three different booleans.

Introduce a new blind string config option that defaults to the
selected floating point type used.

Signed-off-by: Michael Hope <michael.hope@linaro.org>
[yann.morin.1998@anciens.enib.fr: split the original patch]
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

reporter_name="Antony Pavlov"

reporter_url=""

reporter_comment="Experimental toolchain for MIPS32r2"