gdb-server: Create arch-specific structure type for every feature

gdb-server: Create arch-specific structure type for every feature

As it is mentioned here [1] type's ID is unique name within containing feature.

That said if regs of the same type located in different features it's required
to insert type definition at least in each feature.

See more details in discussion here [2].

[1] https://sourceware.org/gdb/onlinedocs/gdb/Target-Description-Format.html#Types
[2] https://github.com/foss-for-synopsys-dwc-arc-processors/openocd/commit/2a5f5125ac8fa0e1359b6be03b209f9f5d1ade82#r33460077

Change-Id: Id92b061cfbf47d5c032a02c2c406b28affd0b02a
Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
Reviewed-on: http://openocd.zylin.com/5179
Tested-by: jenkins
Reviewed-by: Muhammad Omair Javaid <omair.javaid@linaro.org>
Reviewed-by: Matthias Welwarsky <matthias@welwarsky.de>