spl: Split sprintf, strto* from SPL serial in Kconfig

When SPL serial is disabled, callers who need sprintf or strtoul fail
because their inclusion is guarded by CONFIG_SPL_SERIAL_SUPPORT/
CONFIG_TPL_SERIAL_SUPPORT.

Split printf, sprintf and strto into their own entries and then select
all of them if SERIAL_SUPPORT is enabled to match the current behaviour.

Include panic.o unconditionally as it can be called from anywhere which
uses BUG_ON().

Signed-off-by: Alex Kiernan <alex.kiernan@gmail.com>
diff --git a/lib/Makefile b/lib/Makefile
index 35da570..13be8f4 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -88,22 +88,19 @@
 obj-$(CONFIG_TRACE) += trace.o
 obj-$(CONFIG_LIB_UUID) += uuid.o
 obj-$(CONFIG_LIB_RAND) += rand.o
+obj-y += panic.o
 
-ifdef CONFIG_SPL_BUILD
-ifdef CONFIG_TPL_BUILD
-SERIAL_SUPPORT := $(CONFIG_TPL_SERIAL_SUPPORT)
-else
-SERIAL_SUPPORT := $(CONFIG_SPL_SERIAL_SUPPORT)
-endif
+ifeq ($(CONFIG_$(SPL_TPL_)BUILD),y)
 # SPL U-Boot may use full-printf, tiny-printf or none at all
 ifdef CONFIG_USE_TINY_PRINTF
-obj-$(SERIAL_SUPPORT) += tiny-printf.o panic.o strto.o
+obj-$(CONFIG_$(SPL_TPL_)SPRINTF) += tiny-printf.o
 else
-obj-$(SERIAL_SUPPORT) += vsprintf.o panic.o strto.o strmhz.o
+obj-$(CONFIG_$(SPL_TPL_)SPRINTF) += vsprintf.o strmhz.o
 endif
+obj-$(CONFIG_$(SPL_TPL_)STRTO) += strto.o
 else
 # Main U-Boot always uses the full printf support
-obj-y += vsprintf.o panic.o strto.o strmhz.o
+obj-y += vsprintf.o strto.o strmhz.o
 endif
 
 subdir-ccflags-$(CONFIG_CC_OPTIMIZE_LIBS_FOR_SPEED) += -O2