Document requirements for CL_DEVICE_DOUBLE_FP_CONFIG prior to 2.0 (#683)

* Document requirements for CL_DEVICE_DOUBLE_FP_CONFIG prior to 2.0

Fixes #673

Signed-off-by: Kevin Petit <kevin.petit@arm.com>
Change-Id: If163ff3d57f953922baef3c65ca7a2feaff9a23f

* apply wording suggestions

Change-Id: I362651a239538e5317d24c2f04f016f41251311d

Author: kpet

api/opencl_platform_layer.asciidoc

@@ -731,12 +731,22 @@ Also see extension *cl_khr_fp64*.
         double precision floating-point capability is 0.
 
         If double precision is supported by the device, then the minimum
-        double precision floating-point capability is:
+        double precision floating-point capability for OpenCL 2.0 or
+        newer devices is:
 
         {CL_FP_FMA} \| +
         {CL_FP_ROUND_TO_NEAREST} \| +
         {CL_FP_INF_NAN} \| +
         {CL_FP_DENORM}.
+
+        or for OpenCL 1.0, OpenCL 1.1 or OpenCL 1.2 devices:
+
+        {CL_FP_FMA} \| +
+        {CL_FP_ROUND_TO_NEAREST} \| +
+        {CL_FP_ROUND_TO_ZERO} \| +
+        {CL_FP_ROUND_TO_INF} \| +
+        {CL_FP_INF_NAN} \| +
+        {CL_FP_DENORM}.
 | {CL_DEVICE_GLOBAL_MEM_CACHE_TYPE_anchor}
 
 include::{generated}/api/version-notes/CL_DEVICE_GLOBAL_MEM_CACHE_TYPE.asciidoc[]