x86: kprobes: Remove unused macro stack_addr

An unused macro reported by [-Wunused-macros].

This macro is used to access the sp in pt_regs because at that time
x86_32 can only get sp by kernel_stack_pointer(regs).

'3c88c692 ("x86/stackframe/32: Provide consistent pt_regs")'
This commit have unified the pt_regs and from them we can get sp from
pt_regs with regs->sp easily. Nowhere is using this macro anymore.

Refrencing pt_regs directly is more clear. Remove this macro for
code cleaning.

Link: https://lkml.kernel.org/r/20220924072629.104759-1-chenzhongjin@huawei.comSigned-off-by: Chen Zhongjin <chenzhongjin@huawei.com>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

arch/x86/kernel/kprobes/core.c

@@ -59,8 +59,6 @@
 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
 
-#define stack_addr(regs) ((unsigned long *)regs->sp)
-
 #define W(row, b0, b1, b2, b3, b4, b5, b6, b7, b8, b9, ba, bb, bc, bd, be, bf)\
 	(((b0##UL << 0x0)|(b1##UL << 0x1)|(b2##UL << 0x2)|(b3##UL << 0x3) |   \
 	  (b4##UL << 0x4)|(b5##UL << 0x5)|(b6##UL << 0x6)|(b7##UL << 0x7) |   \