ARMC6: Suppress "register deprecated" warning

Lots of target code, STM in particular, uses the `register` keyword, so
it'll take a little while to clean up. In the interim, some builds are
producing a lot of warnings. Suppress the warning for now, as `register`
remains legal C++14 and C11, despite C++14 deprecating it.

C++17 removes `register`, so code will need to be cleaned before any
further C++ version update.

tools/profiles/debug.json

@@ -18,7 +18,7 @@
     "ARMC6": {
         "common": ["-c", "--target=arm-arm-none-eabi", "-mthumb", "-g", "-O1",
                    "-Wno-armcc-pragma-push-pop", "-Wno-armcc-pragma-anon-unions",
-                   "-Wno-reserved-user-defined-literal",
+                   "-Wno-reserved-user-defined-literal", "-Wno-deprecated-register",
                    "-DMULADDC_CANNOT_USE_R7", "-fdata-sections",
                    "-fno-exceptions", "-MMD", "-D_LIBCPP_EXTERN_TEMPLATE(...)=",
                    "-fshort-enums", "-fshort-wchar", "-DMBED_DEBUG",

tools/profiles/develop.json

@@ -17,7 +17,7 @@
     "ARMC6": {
         "common": ["-c", "--target=arm-arm-none-eabi", "-mthumb", "-Os",
                    "-Wno-armcc-pragma-push-pop", "-Wno-armcc-pragma-anon-unions",
-                   "-Wno-reserved-user-defined-literal",
+                   "-Wno-reserved-user-defined-literal", "-Wno-deprecated-register",
                    "-DMULADDC_CANNOT_USE_R7", "-fdata-sections",
                    "-fno-exceptions", "-MMD", "-D_LIBCPP_EXTERN_TEMPLATE(...)=",
                    "-fshort-enums", "-fshort-wchar", "-DMBED_TRAP_ERRORS_ENABLED=1"],

tools/profiles/release.json

@@ -17,7 +17,7 @@
     "ARMC6": {
         "common": ["-c", "--target=arm-arm-none-eabi", "-mthumb", "-Oz",
                    "-Wno-armcc-pragma-push-pop", "-Wno-armcc-pragma-anon-unions",
-                   "-Wno-reserved-user-defined-literal",
+                   "-Wno-reserved-user-defined-literal", "-Wno-deprecated-register",
                    "-DMULADDC_CANNOT_USE_R7", "-fdata-sections",
                    "-fno-exceptions", "-MMD", "-D_LIBCPP_EXTERN_TEMPLATE(...)=",
                    "-fshort-enums", "-fshort-wchar", "-DNDEBUG"],