firmware_loader: make RUST_FW_LOADER_ABSTRACTIONS select FW_LOADER

The use of firmware_loader is an implementation detail of drivers rather
than a dependency. FW_LOADER is typically selected rather than depended
on; the Rust abstractions should do the same thing.

Fixes: de6582833db0 ("rust: add firmware abstractions")
Signed-off-by: Alexandre Courbot <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/base/firmware_loader/Kconfig

···
 config RUST_FW_LOADER_ABSTRACTIONS
 	bool "Rust Firmware Loader abstractions"
 	depends on RUST
-	depends on FW_LOADER=y
+	select FW_LOADER
 	help
 	  This enables the Rust abstractions for the firmware loader API.