scripts/faddr2line: show the code context

Inspired by gdb command 'list', show the code context of target lines.
Here is a example:

$ scripts/faddr2line vmlinux native_write_msr+0x6
native_write_msr+0x6/0x20:
arch_static_branch at arch/x86/include/asm/msr.h:105
100             return EAX_EDX_VAL(val, low, high);
101     }
102
103     static inline void notrace __wrmsr(unsigned int msr, u32 low, u32 high)
104     {
105             asm volatile("1: wrmsr\n"
106                          "2:\n"
107                          _ASM_EXTABLE_HANDLE(1b, 2b, ex_handler_wrmsr_unsafe)
108                          : : "c" (msr), "a"(low), "d" (high) : "memory");
109     }
110
(inlined by) static_key_false at include/linux/jump_label.h:142
137     #define JUMP_TYPE_LINKED        2UL
138     #define JUMP_TYPE_MASK          3UL
139
140     static __always_inline bool static_key_false(struct static_key *key)
141     {
142             return arch_static_branch(key, false);
143     }
144
145     static __always_inline bool s...