That's just really odd, that it's recognizing the APU but not the 7450m. Anyway, just for some more information, what's the output of fglrxinfo, and is Xorg showing any errors?
cat /var/log/Xorg.0.log | grep "(EE)"
fglrxinfo -
display: :0 screen: 0
OpenGL vendor string: ATI Technologies Inc.
OpenGL renderer string: AMD Radeon(TM) HD 6620G
OpenGL version string: 4.1.10665 Compatibility Profile Context
cat /var/log/Xorg.0.log | grep "(EE)"
(WW) warning, (EE) error, (NI) not implemented, (??) unknown.
[ 13584.156] (EE) HP Webcam-101: Couldn't open mtdev device
[ 14471.164] (EE) HP Webcam-101: Couldn't open mtdev device
[ 18305.940] (EE) HP Webcam-101: Couldn't open mtdev device
[ 20260.072] (EE) HP Webcam-101: Couldn't open mtdev device
[ 25316.825] (EE) HP Webcam-101: Couldn't open mtdev device
[ 32542.197] (EE) HP Webcam-101: Couldn't open mtdev device