platform/x86/amd: pmc: Fix memory leak in amd_pmc_stb_debugfs_open_v2()

Function amd_pmc_stb_debugfs_open_v2() may be called when the STB
debug mechanism enabled.

When amd_pmc_send_cmd() fails, the 'buf' needs to be released.

Signed-off-by: Feng Jiang <jiangfeng@kylinos.cn>
Link: https://lore.kernel.org/r/20230412093734.1126410-1-jiangfeng@kylinos.cn
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

Author: flynnjiang

drivers/platform/x86/amd/pmc.c

@@ -265,6 +265,7 @@ static int amd_pmc_stb_debugfs_open_v2(struct inode *inode, struct file *filp)
 	dev->msg_port = 0;
 	if (ret) {
 		dev_err(dev->dev, "error: S2D_NUM_SAMPLES not supported : %d\n", ret);
+		kfree(buf);
 		return ret;
 	}