tests: math: interpolation: disable floating point contraction

This test cannot tolerate any loss of precision, including the one
caused by the compiler contracting floating points operations together,
like in fused multiply-add (FMA). Some toolchains enable FP contraction
by default, so disable it for the specific test and let the user decide
themselves whether precision or performance is needed for their
specific application.

Co-authored-by: Jordan Yates <jordan@embeint.com>
Co-authored-by: Ilya Tagunov <Ilya.Tagunov@synopsys.com>
Signed-off-by: Ilya Tagunov <Ilya.Tagunov@synopsys.com>