Fix TOSA legalization for RSQRT operator
> Its a little bit difficult to evaluate pure on code, was there numerical evaluations done here additionally? Some stats as to them?

For an int8 quantized DETR model, there was sparse -1 discrepancies when comparing the output tensors of tosa.rsqrt and tfl.rsqrt. This patch fixes the reported issue and passes any rsqrt unit tests.

It was necessary to more closely mimic the TFLite kernel's approach to calculating the rsqrt in order to ensure consistency between the two for any input (i.e. perform operations in the quantized type as opposed to in the dequantized type, as previously). Hi @jpienaar Can you please assist on above comments from @jamwar01. Thank you!
More closely match tflite kernel's behaviour

Change-Id: Ibe1a6e24c069beddfb46cf40c665d346b88cf097