update readme for Intel CPU and XPU do not need make csrc codes

Author: jiqing-feng

docs/source/installation.mdx

@@ -336,8 +336,6 @@ The below commands are for Linux. For installing on Windows, please adapt the be
 git clone --depth 1 -b multi-backend-refactor https://github.com/bitsandbytes-foundation/bitsandbytes.git && cd bitsandbytes/
 pip install intel_extension_for_pytorch
 pip install -r requirements-dev.txt
-cmake -DCOMPUTE_BACKEND=cpu -S .
-make
 pip install -e .   # `-e` for "editable" install, when developing BNB (otherwise leave that out)
 ```
 

docs/source/non_cuda_backends.mdx

@@ -33,12 +33,12 @@ The following performance data is collected from Intel 4th Gen Xeon (SPR) platfo
 
 | Data Type | BF16 | INT8 | NF4 | FP4 |
 |---|---|---|---|---|
-| Speed-Up (vs BF16) | 1.0x | 0.6x | 2.3x | 0.03x |
+| Speed-Up (vs BF16) | 1.0x | 0.44x | 1.8x | 0.1x |
 | Memory (GB) | 13.1 | 7.6 | 5.0 | 4.6 |
 
 #### Fine-Tuning (CPU)
 
-| Data Type | AMP BF16 | INT8 | NF4 | FP4 |
+| Data Type | BF16 | INT8 | NF4 | FP4 |
 |---|---|---|---|---|
-| Speed-Up (vs AMP BF16) | 1.0x | 0.38x | 0.07x | 0.07x |
+| Speed-Up (vs BF16) | 1.0x | 0.38x | 0.1x | 0.1x |
 | Memory (GB) | 40 | 9 | 6.6 | 6.6 |