[SYCL][NFC] Make links in README relative to the repository

This should help to get consistent links in the forks.

Signed-off-by: Alexey Bader <[email protected]>

Author: bader

README.md

@@ -7,17 +7,17 @@ Home for Intel LLVM-based projects:
  - SYCL* Compiler and Runtimes - compiler and runtime libraries for SYCL ([https://www.khronos.org/sycl/](https://www.khronos.org/sycl/)). See **sycl** branch.
 
 ## License
-See [LICENSE.txt](https://github.com/intel/llvm/blob/intel/llvm/LICENSE.TXT) for details.
+See [LICENSE.txt](sycl/LICENSE.TXT) for details.
 
 
 ## Contributing
-See [CONTRIBUTING.md](https://github.com/intel/llvm/blob/intel/CONTRIBUTING.md) for details.
+See [CONTRIBUTING.md](CONTRIBUTING.md) for details.
 
 ## Sub-projects Documentation
- - SYCL Compiler and Runtimes - See [GetStartedWithSYCLCompiler.md](https://github.com/intel/llvm/blob/sycl/sycl/doc/GetStartedWithSYCLCompiler.md)
+ - SYCL Compiler and Runtimes - See [GetStartedWithSYCLCompiler.md](sycl/doc/GetStartedWithSYCLCompiler.md)
 
 *Other names and brands may be claimed as the property of others.
 
 ## SYCL Extension Proposal Documents
 
-See [sycl/doc/extensions](https://github.com/intel/llvm/tree/sycl/sycl/doc/extensions)
+See [sycl/doc/extensions](sycl/doc/extensions)