fs/procfs: fix output format of fd info

[JianyuWang0623]

Summary

Fix output format of fd info. Refered to PRINTF(3), the [v]snprintf returns the number of characters printed (excluding the null byte used to end output to strings).

Upon successful return, these functions return the number of characters printed (excluding the null byte used to end output to strings). -- PRINTF(3)

Impact

• fs/procfs

Testing

• Currently

1. Extra blank at line start, e.g. fd num 1 and below
2. Truncated print, see fd num 3, missing end bracked "]"

nsh> fdinfo 9

FD  OFLAGS  TYPE POS       PATH           
0   3       1    0         /dev/console 
 1   3       1    0         /dev/console 
 2   3       1    0         /dev/console 
 3   3       9    0         tcp:[0.0.0.0:5554<->0.0.0.0:0, st 01, flg 31
 4   1089    1    0         /dev/fastboot/ep
 5   1090    1    0         /dev/fastboot/ep
 6   0       1    0                      
 nsh> 
nsh>

• With this patch

nsh> fdinfo 9

FD  OFLAGS  TYPE POS       PATH           BACKTRACE
0   3       1    0         /dev/console  
1   3       1    0         /dev/console  
2   3       1    0         /dev/console  
3   3       9    0         tcp:[0.0.0.0:5554<->0.0.0.0:0, st 01, flg 31]
4   1089    1    0         /dev/fastboot/ep2
5   1090    1    0         /dev/fastboot/ep1
6   0       1    0                       
nsh>