drm/amdgpu: fix description of vm_size module parameter (v2)

default is 8GB, not 4GB.

v2: fix fallback setting when the user provides an invalid input

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
index 6edacce..56da962 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
@@ -128,7 +128,7 @@
 MODULE_PARM_DESC(deep_color, "Deep Color support (1 = enable, 0 = disable (default))");
 module_param_named(deep_color, amdgpu_deep_color, int, 0444);
 
-MODULE_PARM_DESC(vm_size, "VM address space size in gigabytes (default 4GB)");
+MODULE_PARM_DESC(vm_size, "VM address space size in gigabytes (default 8GB)");
 module_param_named(vm_size, amdgpu_vm_size, int, 0444);
 
 MODULE_PARM_DESC(vm_block_size, "VM page table size in bits (default depending on vm_size)");