kgdb: support for ARCH=arm

This patch adds the ARCH=arm specific a kgdb backend, originally
written by Deepak Saxena <dsaxena@plexity.net> and George Davis
<gdavis@mvista.com>.  Geoff Levand <geoffrey.levand@am.sony.com>,
Nicolas Pitre, Manish Lachwani, and Jason Wessel have contributed
various fixups here as well.

The KGDB patch makes one change to the core ARM architecture such that
the traps are initialized early for use with the debugger or other
subsystems.

[ mingo@elte.hu: small cleanups. ]
[ ben-linux@fluff.org: fixed early_trap_init ]

Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Acked-by: Deepak Saxena <dsaxena@plexity.net>
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index c7ad324..d048f68 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -12,6 +12,7 @@
 	select RTC_LIB
 	select SYS_SUPPORTS_APM_EMULATION
 	select HAVE_OPROFILE
+	select HAVE_ARCH_KGDB
 	select HAVE_KPROBES if (!XIP_KERNEL)
 	select HAVE_KRETPROBES if (HAVE_KPROBES)
 	select HAVE_FTRACE if (!XIP_KERNEL)