fix(semihosting): fix seek call failure check

The code checks that the semihosting seek call return value is not
zero instead of a negative value when there is an error condition.
This defect has been fixed.

In [1], possible return values for semihosting seek calls are
mentioned.

[1]: https://github.com/ARM-software/abi-aa/blob/main/semihosting/


semihosting.rst#sys-seek-0x0a

Change-Id: I70f09e98323e9c5bf4eeda322ac065e855e256fc
Signed-off-by: Manish V Badarkhe <Manish.Badarkhe@arm.com>