Remove PC from syscall_next_pc

Remove PC from syscall_next_pc

Method syscall_next_pc of struct arm_get_next_pcs_ops has an argument
PC, which is not necessary, because PC can be got from regcache in
'struct arm_get_next_pcs'.  This patch removes the PC argument of
syscall_next_pc.

gdb:

2016-02-16  Yao Qi  <yao.qi@linaro.org>

	* arch/arm-get-next-pcs.h (struct arm_get_next_pcs_ops)
	<syscall_next_pc>: Remove argument PC.  Callers updated.
	* arm-linux-tdep.c (arm_linux_get_next_pcs_syscall_next_pc):
	Remove argument PC.  Get pc from regcache_read_pc.
	* arm-tdep.c (arm_get_next_pcs_syscall_next_pc): Remove
	argument PC.

gdb/gdbserver:

2016-02-16  Yao Qi  <yao.qi@linaro.org>

	* linux-arm-low.c (get_next_pcs_syscall_next_pc): Remove argument
	PC.  Get pc from regcache_read_pc.