minui: GRSurface::Create() computes data_size on its own.

GRSurface::Create() doesn't need to rely on caller specifying the buffer
size, as it can compute that info based on the given args.

This CL also uses `size_t` for all the parameters in
GRSurface::Create().

Test: Run recovery_unit_test on marlin.
Test: Build and boot into blueline recovery. `Run graphics test`.
Test: Build and boot into blueline charger mode.
Change-Id: Idec9381079196abf13553a475006fefcfca10950