kgdbts: Use HW breakpoints with CONFIG_DEBUG_RODATA

Whenever CONFIG_DEBUG_RODATA is set in the kernel config many kernel
text sections become read-only, and the use of software breakpoints in
the kgdb tests will cause the kernel to fail to complete the start up.

Until such time that there is an official API for modifying read-only
text sections hardware breakpoints must be used to run the do_fork or
sys_open tests or the tests get skipped.

Also fix the duplicated include reported by:
Huang Weiyi <weiyi.huang@gmail.com>

Signed-off-by: Jason Wessel <jason.wessel@windriver.com>