arm: fix reg num for Monitor mode

arm: fix reg num for Monitor mode

Commit 2efb1f14f611 ("Add GDB remote target description support
for ARM4") inserts two additional registers "sp" and "lr" in the
table arm_core_regs[], thus shifting by two the position of the
last three registers already present
	"sp_mon" moved from index 37 to 39
	"lr_mon" moved from index 38 to 40
	"spsr_mon" moved from index 39 to 41
Part of the code is updated (e.g. enum defining ARM_SPSR_MON and
array arm_mon_indices[]), but it's missing the update of mapping
in armv4_5_core_reg_map[].

Fix armv4_5_core_reg_map[].

Change-Id: I0bdf766183392eb738206b876cd9559aacc29fa0
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Fixes: 2efb1f14f611 ("Add GDB remote target description support for ARM4")
Reviewed-on: http://openocd.zylin.com/5257
Tested-by: jenkins