Python: pyusb: Clarify BSD license variant

The License of python pyusb is BSD-3-Clause.

Signed-off-by: Christophe Priouzeau <christophe.priouzeau@st.com>
Signed-off-by: Khem Raj <raj.khem@gmail.com>

meta-python/recipes-devtools/python/python-pyusb.inc

@@ -1,6 +1,6 @@
 SUMMARY = "PyUSB provides USB access on the Python language"
 HOMEPAGE = "http://pyusb.sourceforge.net/"
-LICENSE = "BSD"
+LICENSE = "BSD-3-Clause"
 LIC_FILES_CHKSUM = "file://LICENSE;md5=51691ed11cc2c7ae93e383f60ed49b0f"
 DEPENDS += "libusb1"