reset: sti: simplify driver's config and build

With commit 64933513e461 ("reset: sti: Remove STiH415/6 reset support"),
there is only one sti reset driver left and there no need to define a
dedicated config STI_RESET_SYSCFG, which is selected by the config for the
STiH407 reset driver.

Simply add reset-syscfg.c to the build for the STiH407 reset driver.

Signed-off-by: Lukas Bulwahn <[e-mail]>
Reviewed-by: Patrice Chotard <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Philipp Zabel <[e-mail]>

drivers/reset/sti/Kconfig

···
 # SPDX-License-Identifier: GPL-2.0-only
 if ARCH_STI
 
-config STI_RESET_SYSCFG
-	bool
-
 config STIH407_RESET
 	bool
-	select STI_RESET_SYSCFG
 
 endif

drivers/reset/sti/Makefile

···
 # SPDX-License-Identifier: GPL-2.0-only
-obj-$(CONFIG_STI_RESET_SYSCFG) += reset-syscfg.o
-
-obj-$(CONFIG_STIH407_RESET) += reset-stih407.o
+obj-$(CONFIG_STIH407_RESET) += reset-stih407.o reset-syscfg.o