firmware_loader: rework crypto dependencies

The crypto dependencies for the firmwware loader are incomplete,
in particular a built-in FW_LOADER fails to link against a modular
crypto hash driver:

ld.lld: error: undefined symbol: crypto_alloc_shash
ld.lld: error: undefined symbol: crypto_shash_digest
ld.lld: error: undefined symbol: crypto_destroy_tfm
>>> referenced by main.c
>>> drivers/base/firmware_loader/main.o:(fw_log_firmware_info) in archive vmlinux.a

Rework this to use the usual 'select' from the driver module,
to respect the built-in vs module dependencies, and add a
more verbose crypto dependency to the debug option to prevent
configurations that lead to a link failure.

Fixes: 02fe26f25325 ("firmware_loader: Add debug message with checksum for FW file")
Reviewed-by: Amadeusz Sławiński <[e-mail]>
Acked-by: Herbert Xu <[e-mail]>
Acked-by: Luis Chamberlain <[e-mail]>
Signed-off-by: Arnd Bergmann <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/base/firmware_loader/Kconfig

···
 
 config FW_LOADER
 	tristate "Firmware loading facility" if EXPERT
+	select CRYPTO_HASH if FW_LOADER_DEBUG
+	select CRYPTO_SHA256 if FW_LOADER_DEBUG
 	default y
 	help
 	  This enables the firmware loading facility in the kernel. The kernel
···
 
 config FW_LOADER_DEBUG
 	bool "Log filenames and checksums for loaded firmware"
+	depends on CRYPTO = FW_LOADER || CRYPTO=y
 	depends on DYNAMIC_DEBUG
 	depends on FW_LOADER
-	depends on CRYPTO
-	depends on CRYPTO_SHA256
 	default FW_LOADER
 	help
 	  Select this option to use dynamic debug to log firmware filenames and