python: Create requirements.txt files for each "project"

Rather than have a requirements.txt file that's shared between multiple
python projects within U-Boot, create one for each using "pipreqs".

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/tools/u_boot_pylib/requirements.txt b/tools/u_boot_pylib/requirements.txt
new file mode 100644
index 0000000..1087e6f
--- /dev/null
+++ b/tools/u_boot_pylib/requirements.txt
@@ -0,0 +1 @@
+concurrencytest==0.1.2