Rename dequantization template parameters (#7976)
Followup to https://github.com/deepspeedai/DeepSpeed/pull/7973 for #7971
The naming of q_mantisa_bits and mantisa_bits was swapped. The
invocation set:
```
q_mantisa_bits = mantisa
_mantisa_bits = CONST_Q_MANTISA_BITS
_exponent_bits = CONST_Q_EXPONENT_BITS
```
so correct them by swapping the names back.
I noticed that the code needs a thorough review because multiple places
look suspicious:
```
// Why the default args? They seem to not even be matching (16 != 3+4+1)
int total_q_bits = 16,
int q_mantisa_bits = 3,
int q_exponent_bits = 4>
// Why recompute if there is a total_q_bits template?
constexpr int quantized_bits = q_mantisa_bits + q_exponent_bits + 1;
// Likely wrong: total_q_bits < mantisa_bits --> negative bits? Likely caused by wrong naming
constexpr int q_exponent_bits = total_q_bits - mantisa_bits - 1;
// should likey use a `q_` prefix not `_`
constexpr uint16_t _mantisa_mask = (1 << q_mantisa_bits) - 1;
constexpr uint16_t _exponent_mask = ((1 << q_exponent_bits) - 1) << q_mantisa_bits;
constexpr uint16_t _sign_mask = 1U << (q_mantisa_bits + q_exponent_bits);
```
cc @Cursx
Signed-off-by: Alexander Grund <alexander.grund@tu-dresden.de>
