drm/lima: fix a memleak in lima_heap_alloc

When lima_vm_map_bo fails, the resources need to be deallocated, or
there will be memleaks.

Fixes: 6aebc51d ("drm/lima: support heap buffer creation")
Signed-off-by: Zhipeng Lu <alexious@zju.edu.cn>
Signed-off-by: Qiang Yu <yuq825@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240117071328.3811480-1-alexious@zju.edu.cn