COMPMID-1086: Optimizing GCGEMM - Add helpers to get target GPU information

This patch moves some of the helper functions in CLHelpers.[h,cpp] to
GPUTarget.[h,cpp] in order to make them avaialable to both CL and GLES backends.

Change-Id: Ib89b05a2084b73eb643b32fac13b8367cc80b6a5
Reviewed-on: https://eu-gerrit-1.euhpc.arm.com/128988
Tested-by: Jenkins <bsgcomp@arm.com>
Reviewed-by: Anthony Barbier <anthony.barbier@arm.com>
diff --git a/src/core/GLES_COMPUTE/gl_entries.in b/src/core/GLES_COMPUTE/gl_entries.in
index 15ce8ee..17e3aee 100644
--- a/src/core/GLES_COMPUTE/gl_entries.in
+++ b/src/core/GLES_COMPUTE/gl_entries.in
@@ -61,3 +61,4 @@
 GL_ENTRY(glDeleteFramebuffers)
 GL_ENTRY(glBindFramebuffer)
 GL_ENTRY(glFramebufferTexture2D)
+GL_ENTRY(glGetString)