spl: kconfig: separate sysreset and firmware drivers from misc

This adds separate kconfig options for drivers/sysreset and
drivers/firmware.

Up to now, CONFIG_SPL_DRIVERS_MISC_SUPPORT added drivers/misc to SPL
build but also added drivers/firmware and drivers/sysreset at the same
time.

Since that is confusing, this patch uses CONFIG_SPL_SYSRESET for
drivers/sysreset and adds CONFIG_SPL_FIRMWARE for
drivers/firmware (and accordingly for the TPL options).

CONFIG_SPL_DRIVERS_MISC_SUPPORT stays for including drivers/misc into
the SPL build (and accordingly for TPL) since there are boards using
non-DM (non UCLASS_MISC) files from drivers/misc. Such boards don't
have CONFIG_SPL_MISC enabled, so cannot use this to include
drivers/misc into the SPL build.

Signed-off-by: Simon Goldschmidt <simon.k.r.goldschmidt@gmail.com>