[Bugfix]Modify NPU rotary encoding parameter fields，fix RopeOperation setup failed in condition of self.rotary_dim < self.head_size (#6310)

### What this PR does / why we need it?
change self.head_size to self.rotary_dim.
only the rotary part is processed here, the dimension should be rotary_dim.

Fix bug #6060

### Does this PR introduce _any_ user-facing change?
No

### How was this patch tested?
Only a small section of code was modified to adjust the parameters, and
all standard tests were passed.

- vLLM version: v0.14.1
- vLLM main:
dc917cceb8

Signed-off-by: fengshi666 <fengshi666@adsl-99-12-210-25.dsl.hstntx.sbcglobal.net>
Co-authored-by: fengshi666 <fengshi666@adsl-99-12-210-25.dsl.hstntx.sbcglobal.net>

vllm_ascend/ops/rotary_embedding.py

@@ -240,11 +240,13 @@ def _rope_forward_oot(
                 k_pass = key[..., self.rotary_dim:]
                 q_rot = q_rot.contiguous().view(num_tokens, -1)
                 k_rot = k_rot.contiguous().view(num_tokens, -1)
+                # only the rotary part is processed here,
+                # the dimension should be rotary_dim
                 torch_npu._npu_rotary_embedding(
                     positions,
                     q_rot,
                     k_rot,
-                    self.head_size,
+                    self.rotary_dim,
                     self.cos_sin_cache,
                     is_neox_style,
                 )