accel/amdxdna: Declare npu6_dev_priv as static

Fix sparse warning:
symbol 'npu6_dev_priv' was not declared. Should it be static?

Fixes: 273b5176ac17 ("accel/amdxdna: Add RyzenAI-npu6 support")
Reported-by: kernel test robot <[e-mail]>
Closes: https://lore.kernel.org/oe-kbuild-all/[e-mail]/
Signed-off-by: Lizhi Hou <[e-mail]>
Reviewed-by: Mario Limonciello <[e-mail]>
Signed-off-by: Mario Limonciello <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/accel/amdxdna/npu6_regs.c

···
 #define NPU6_SMU_BAR_BASE	MMNPU_APERTURE4_BASE
 #define NPU6_SRAM_BAR_BASE	MMNPU_APERTURE1_BASE
 
-const struct amdxdna_dev_priv npu6_dev_priv = {
+static const struct amdxdna_dev_priv npu6_dev_priv = {
 	.fw_path        = "amdnpu/17f0_10/npu.sbin",
 	.protocol_major = 0x6,
 	.protocol_minor = 12,