fix: semihosting_fileio display the unsupported info (#699)

the abnormal info display below:
semihosting: unsupported call 0
semihosting: unsupported call 0
semihosting: unsupported call 0
semihosting: unsupported call 0
semihosting: unsupported call 0
semihosting: unsupported call 0
semihosting: unsupported call 0
semihosting: unsupported call 0
semihosting: unsupported call 0
semihosting: unsupported call 0
semihosting: unsupported call 0

the PC did not plus 4 before resume, which cause this
abnormal info popup.

Change-Id: I15c1e7426f1925e78f607c566976f9352216506f
Signed-off-by: Wu Zhigang <zhigang.wu@starfivetech.com>

Co-authored-by: Wu Zhigang <zhigang.wu@starfivetech.com>