wsl/hsakmt: Remove fn_amdgpu_device_get_fd in openclose.cpp

There are already relevant implementations in this patch
dcf0fa2 ("wsl/thunk: implement drm interfaces for dropping libdrm*")

Signed-off-by: Horatio Zhang <Hongkun.Zhang@amd.com>
Reviewed-by: Flora Cui <flora.cui@amd.com>
Part-of: <http://10.67.69.192/wsl/libhsakmt/-/merge_requests/37>

openclose.cpp

@@ -37,8 +37,6 @@
 #include "inc/hsa/hsa.h"
 #include "inc/hsa/hsa_ven_amd_loader.h"
 
-int (*fn_amdgpu_device_get_fd)(HsaAMDGPUDeviceHandle device_handle);
-
 hsa_signal_value_t (*fn_hsa_signal_load_relaxed)(hsa_signal_t signal);
 hsa_signal_value_t (*fn_hsa_signal_wait_relaxed)(
     hsa_signal_t signal, hsa_signal_condition_t condition,