tools: PCI: Handle pcitest.sh independently from pcitest

Handling pcitest.sh along with pcitest (obtained by compiling
pcitest.c) results in pcitest.sh getting removed inadvertently
while "make -C tools/pci clean".

Fix it by handling pcitest.sh independently of pcitest.

Fixes: 1ce78ce0 ("tools: PCI: Change pcitest compiling process")
Reported-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Gustavo Pimentel <gustavo.pimentel@synopsys.com>