cxl: fix CONFIG_FW_LOADER dependency

When FW_LOADER is disabled, cxl fails to link:

arm-linux-gnueabi-ld: drivers/cxl/core/memdev.o: in function `cxl_memdev_setup_fw_upload':
memdev.c:(.text+0x90e): undefined reference to `firmware_upload_register'
memdev.c:(.text+0x93c): undefined reference to `firmware_upload_unregister'

In order to use the firmware_upload_register() function, both FW_LOADER
and FW_UPLOAD have to be enabled, which is a bit confusing. In addition,
the dependency is on the wrong symbol, as the caller is part of the
cxl_core.ko module, not the cxl_mem.ko module.

Fixes: 9521875b

 ("cxl: add a firmware update mechanism using the sysfs firmware loader")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20230703112928.332321-1-arnd@kernel.org
Reviewed-by: Xiao Yang <yangx.jy@fujitsu.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>