frameworks/base/packages/SystemUI: Modified roaming icon image files

Modified the image colour of the CDMA Roaming icon.
Prior to this the roaming triangle was in black and was not visible
against the background in StatusBar annunciator area.

CRs-Fixed: 273336
(cherry picked from commit c27328c3d25e3d8e0c07961acb0b72c508a81115)

Change-Id: I242ccd94c7b7678896b8928c59ac1fc308c7a668