tilegx has 64 registers, to show them in row will be not very convinent 
to explore,
so we improve this by showing them in columns.

(gdb) info registers
r0   0x0000000000000001    r19  0x0000000000000000    r38 0x0000000000000040
r1   0x000001ffffc7f458         r20  0x000001ffffc7f278         r39 
0x0000000000000000
r2   0x000001ffffc7f468         r21  0x000001ffffc7f298         r40 
0x000000000015b3e8
r3   0x0000000000010720    r22  0x000001ffffc7f280         r41 
0x000000000015882c
...
...

gdb/ChangeLog:

        * tilegx-tdep.c (tilegx_print_registers_info): New function.
        show registers in columns.

please review.

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Regards,
Jiong
Tilera Corporation.