math: p_ln_f32: Use right type for constants
math: p_ln_f32: Use right type for constants

Use PCONST to get right type for M_LN2

Signed-off-by: Ola Jeppsson <793f970c52ded1276b9264c742f19d1888cbaf73@adapteva.com>

aolofsson/pal,parallella/pal,aolofsson/pal,parallella/pal,aolofsson/pal,aolofsson/pal,parallella/pal,parallella/pal,parallella/pal