vc04_services/vc-sm-cma: Switch one-bit bitfields to bool

Clang 16 warns:

../drivers/staging/vc04_services/vc-sm-cma/vc_sm.c:816:19: warning: implicit truncation from 'int' to a one-bit wide bit-field changes value from 1 to -1 [-Wsingle-bit-bitfield-constant-conversion]
        buffer->imported = 1;
                         ^ ~
../drivers/staging/vc04_services/vc-sm-cma/vc_sm.c:822:17: warning: implicit truncation from 'int' to a one-bit wide bit-field changes value from 1 to -1 [-Wsingle-bit-bitfield-constant-conversion]
        buffer->in_use = 1;
                       ^ ~
2 warnings generated.

Signed-off-by: Alexander Winkowski <dereference23@outlook.com>