whisper : fixed crash in GPU device selection on multi-GPU systems

[Dw9]

Note that ffmpeg has recently integrated whisper FFmpeg/FFmpeg@13ce36f; testing on a multi-card machine with a non-zero card will cause a crash

./ffmpeg -i ../test.wav -vn -af "whisper=model=../whisper.cpp/models/ggml-large-v3-turbo.bin
:language=zh
:gpu_device=1
:queue=3
:destination=output.srt
:format=srt" -f null -
ffmpeg version N-120674-g5733e08c97 Copyright (c) 2000-2025 the FFmpeg developers
built with gcc 11 (Ubuntu 11.4.0-1ubuntu1~22.04)
configuration: --disable-x86asm --enable-whisper
libavutil 60. 9.100 / 60. 9.100
libavcodec 62. 12.100 / 62. 12.100
libavformat 62. 4.100 / 62. 4.100
libavdevice 62. 2.100 / 62. 2.100
libavfilter 11. 5.100 / 11. 5.100
libswscale 9. 2.100 / 9. 2.100
libswresample 6. 2.100 / 6. 2.100
[aist#0:0/pcm_s16le @ 0x5568ff8dabc0] Guessed Channel Layout: mono
Input #0, wav, from '../test.wav':
Metadata:
encoder : Lavf58.76.100
Duration: 00:00:58.62, bitrate: 256 kb/s
Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 16000 Hz, mono, s16, 256 kb/s
[Parsed_whisper_0 @ 0x5568ff8be280] whisper gpu 1 gpu-id:1
/home/zhibo/dw/whisper.cpp/ggml/src/ggml-backend.cpp:736: pre-allocated tensor (leaf_0) in a buffer (CUDA0) that cannot run the operation (NONE)
/usr/local/lib/libggml-base.so(+0x16ceb)[0x7fd221397ceb]
/usr/local/lib/libggml-base.so(ggml_print_backtrace+0x21f)[0x7fd22139814f]
/usr/local/lib/libggml-base.so(ggml_abort+0x152)[0x7fd221398322]
/usr/local/lib/libggml-base.so(+0x2c174)[0x7fd2213ad174]
/usr/local/lib/libggml-base.so(+0x2d846)[0x7fd2213ae846]
/usr/local/lib/libggml-base.so(ggml_backend_sched_alloc_graph+0xcd)[0x7fd2213b007d]
/usr/local/lib/libwhisper.so.1(+0x30163)[0x7fd232886163]
/usr/local/lib/libwhisper.so.1(whisper_init_state+0x99a)[0x7fd23288b1da]
/usr/local/lib/libwhisper.so.1(whisper_init_from_file_with_params+0x37)[0x7fd2328953d7]
./ffmpeg(+0x41cf6a)[0x5568d4beef6a]
./ffmpeg(+0x1f9dcf)[0x5568d49cbdcf]
./ffmpeg(+0x20f928)[0x5568d49e1928]
./ffmpeg(+0x21025b)[0x5568d49e225b]
./ffmpeg(+0x1a5e11)[0x5568d4977e11]
./ffmpeg(+0x1a95bf)[0x5568d497b5bf]
./ffmpeg(+0x1ab6f3)[0x5568d497d6f3]
./ffmpeg(+0x1b11f0)[0x5568d49831f0]
./ffmpeg(+0x1b2b9f)[0x5568d4984b9f]
./ffmpeg(+0x1b30e9)[0x5568d49850e9]
./ffmpeg(+0x1b3b39)[0x5568d4985b39]
./ffmpeg(+0x1b7a97)[0x5568d4989a97]
./ffmpeg(+0x1baecb)[0x5568d498cecb]
./ffmpeg(+0x199a48)[0x5568d496ba48]
/lib/x86_64-linux-gnu/libc.so.6(+0x29d90)[0x7fd232656d90]
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0x80)[0x7fd232656e40]
./ffmpeg(+0x19a565)[0x5568d496c565]