math: Optimize frexpl (intel96) with fast path for normal numbers

math: Optimize frexpl (intel96) with fast path for normal numbers

Add fast path optimization for frexpl (80-bit x87 extended precision) using
a single unsigned comparison to identify normal floating-point numbers and
return immediately via arithmetic on the exponent field.

The implementation uses arithmetic operations (se - ex ) to
adjust the exponent directly, which is simpler than bit masking. For subnormals,
the traditional multiply-based normalization is retained as it handles the
split word format more reliably.

The zero/infinity/NaN check groups these special cases together for better
branch prediction.

Benchmark results on Intel Core i9-13900H (13th Gen):
  Baseline:     25.543 ns/op
  Optimized:    25.531 ns/op
  Speedup:      1.00x (neutral)
  Zero:         17.774 ns/op
  Denormal:     23.900 ns/op

Signed-off-by: Osama Abdelkader <osama.abdelkader@gmail.com>
Reviewed-by: Wilco Dijkstra  <Wilco.Dijkstra@arm.com>