Replace call of celt_inner_prod_c() (step 1)

Should call celt_inner_prod().

This change is bit exact as original, except for x86 floating-point.
In x86 floating-point, it calls celt_inner_prod_sse() which may have
different output with the change of floating-point operations' orders.

Change-Id: Ia2381e2e198a84296ac28305183f15be842b3454

Signed-off-by: Jean-Marc Valin <jmvalin@jmvalin.ca>