SWDEV-425678 - Fix build failure in HIP samples

- Due to file reorg path changes cmake fails at find_package(hip) unless CMAKE_PREFIX_PATH is set explicitly
- Update CMakeLists.txt to set CMAKE_PREFIX_PATH
- Update Readme

Change-Id: Ibdb4419efcdd6583b059a728e48dfdb8f927a48b

samples/0_Intro/bit_extract/CMakeLists.txt

@@ -30,6 +30,14 @@ if(${__HIP_ENABLE_PCH})
   add_definitions(-D__HIP_ENABLE_PCH)
 endif()
 
+if(UNIX)
+  if(NOT DEFINED ROCM_PATH)
+    set(ROCM_PATH "/opt/rocm" CACHE STRING "Default ROCM installation directory.")
+  endif()
+  # Search for rocm in common locations
+  list(APPEND CMAKE_PREFIX_PATH ${ROCM_PATH})
+endif()
+
 # Find hip
 find_package(hip)