buffer: introduce sancus_buffer_sparse() to increase len safely
buffer: introduce sancus_buffer_sparse() to increase len safely

Signed-off-by: Alejandro Mery <cdfd70a51550235bbe9d06a3549b54fb5429c504@linux.com>

sancus-project/sancus-core,sancus-project/sancus-core,sancus-project/sancus-core