bus: mhi: ep: Test for non-zero return value where applicable

bus: mhi: ep: Test for non-zero return value where applicable

Instead of testing for negative error code, just test for non-zero return
for cases where there is no positive return value. This helps to maintain
code uniformity.

No functional change.

Reported-by: Bjorn Helgaas <helgaas@kernel.org>
Closes: https://lore.kernel.org/linux-pci/20260227191510.GA3904799@bhelgaas
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@oss.qualcomm.com>
Link: https://patch.msgid.link/20260302055021.8616-1-manivannan.sadhasivam@oss.qualcomm.com