[SYCL][Doc] Intel's Extension to Set Kernel Cache Configuration (#2993)

* This proposal details what is required to provide users the ability to set the kernel cache configuration.

Signed-off-by: Gail Lyons <[email protected]>

Author: glyons-intel

sycl/doc/extensions/IntelGPU/IntelGPUKernelCache.md

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+# SYCL(TM) Proposal: Intel's Extension to Set Kernel Cache Configuration
+
+
+**NOTE**: Khronos(R) is a registered trademark and SYCL(TM) is a trademark of the Khronos Group, Inc.
+
+A new API will be added to set the cache configuration in the kernel.  This information will be useful to developers tuning specifically for those devices.
+
+This proposal details what is required to provide this API as a SYCL extensions.
+
+## Feature Test Macro ##
+
+The Feature Test Macro will be defined as:
+
+    #define SYCL_EXT_INTEL_KERNEL_CACHE_CONFIG 1
+
+
+# Setting the Kernel Cache Configuration #
+
+The cache configuration of the kernel can be modified to favor large shared local memory (SLM) or large data.  This API gives users a way to do request this change.
+
+The new API is only available when using the Level Zero platform.
+
+``` C++
+enum class kernel_cache_config {
+  cache_large_slm,
+  cache_large_data
+};
+
+cl::sycl::kernel::set_cache_config(const kernel_cache_config);
+```
+
+
+## Example Usage ##
+
+``` C++
+  // Use Feature Test macro to see if this extension is supported.
+#ifdef SYCL_EXT_INTEL_KERNEL_CACHE_CONFIG
+    // Configure the kernel to use large SLM.
+    krn.set_cache_config(cache_large_slm);
+#endif
+
+```