ASoC: Intel: Fix audio crash due to negative address offset

There were occasional ADSP crash during reboot testing:

[   11.883364] BUG: unable to handle kernel paging request at ffffc90121700000
[   11.883380] IP: [<ffffffffc024d8bc>] sst_module_insert_fixed_block+0x24f/0x26d [snd_soc_sst_dsp]
[   11.883397] PGD 7800b067 PUD 0
[   11.883405] Oops: 0002 [#1] SMP
[   11.886418] gsmi: Log Shutdown Reason 0x03

The virtual address, ffffc90121700000, was out of range. The virtual
address is calculated by adding LPE base address with an offset:

sst_memcpy32(dsp->addr.lpe + data->offset, data->data, data->size);

The offset is calculated in sst_byt_parse_module, by subtraction of
two virtual addresses dsp->addr.fw_ext and dsp->addr.lpe:

block_data.offset = block->ram_offset + (dsp->addr.fw_ext - dsp->addr.lpe);

These virtual addresses are assigned by kernel from ioremap:

sst->addr.lpe = ioremap(pdata->lpe_base, pdata->lpe_size);
sst->addr.fw_ext = ioremap(pdata->fw_base, pdata->fw_size);

In current driver code, offset is defined as unsigned int32:

struct sst_module_data {
...
	u32 offset;		/* offset in FW file */
};

Most of the time kernel assigned virtual addresses with addr.fw_ext
greater than addr.lpe. But sometimes it was the other way round.

Fix the problem by declaring offset as signed int32_t.
Signed-off-by: Wenkai Du <wenkai.du@intel.com>
Signed-off-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Signed-off-by: Mark Brown <broonie@linaro.org>

sound/soc/intel/sst-dsp-priv.h

@@ -136,7 +136,7 @@ struct sst_module_data {
 	enum sst_data_type data_type;	/* type of module data */
 
 	u32 size;		/* size in bytes */
-	u32 offset;		/* offset in FW file */
+	int32_t offset;		/* offset in FW file */
 	u32 data_offset;	/* offset in ADSP memory space */
 	void *data;		/* module data */
 };