tools: PCI: Fix compiler warning in pcitest

Fix the following compiler warning in pcitest:

pcitest.c: In function main:
pcitest.c:214:4: warning: too many arguments for
format [-Wformat-extra-args]
    "usage: %s [options]\n"

Fixes: fbca0b284b ("tools: PCI: Add 'h' in optstring of getopt()")
Signed-off-by: Alan Mikhak <alan.mikhak@sifive.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Paul Walmsley <paul.walmsley@sifive.com>

tools/pci/pcitest.c

@@ -223,7 +223,7 @@ int main(int argc, char **argv)
 			"\t-r			Read buffer test\n"
 			"\t-w			Write buffer test\n"
 			"\t-c			Copy buffer test\n"
-			"\t-s <size>		Size of buffer {default: 100KB}\n",
+			"\t-s <size>		Size of buffer {default: 100KB}\n"
 			"\t-h			Print this help message\n",
 			argv[0]);
 		return -EINVAL;