msm_rmnet_sdio: Fix potential memory corruption

Usage of legacy string manipulation function sprintf could lead to
memory corruption as the number of bytes to be written to the
destination is not bounded. Replace sprintf with snprintf where the
number of bytes to be written is explicitly specified.

CRs-fixed: 672202
Change-Id: Ic26bea1ddf9570a4970fc8c4373b066aa385e427
Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>