Fix heap-buffer-overflow

Cast signed char to unsigned char to avoid sprintf doing sign extension
for %x.

Test: build
Bug: 75983919
Merged-In: I6685a77ac1c832d8dd83beafd7e463d56fab77d3
Change-Id: I6685a77ac1c832d8dd83beafd7e463d56fab77d3
(cherry picked from commit 9caabc0c0a82a8d65d62b2607d3d0e81ebe928f4)
1 file changed