lmb: Fix LMB_MEMORY_REGIONS flag usage

Remove test on CONFIG_LMB_MEMORY_REGIONS introduced by commit
7c1860fce4e3 ("lmb: Fix lmb property's defination under struct lmb").

This code in lmb_init() is strange, because if CONFIG_LMB_USE_MAX_REGIONS
and CONFIG_LMB_MEMORY_REGIONS are not defined, the implicit #else is empty
and the required initialization is not done:
lmb->memory.max = ?
lmb->reserved.max = ?

But this setting is not possible:
- CONFIG_LMB_USE_MAX_REGIONS not defined
- CONFIG_LMB_MEMORY_REGIONS not defined
because CONFIG_LMB_MEMORY_REGIONS and CONFIG_LMB_RESERVED_REGIONS are
defined as soon as the CONFIG_LMB_USE_MAX_REGIONS is not defined.

This patch removes this impossible case #elif and I add some
explanation in lmb.h to explain why in the struct lmb {} the lmb
property is defined if CONFIG_LMB_MEMORY_REGIONS is NOT defined.

This patch also removes CONFIG_LMB_XXX dependency on CONFIG_LMB as these
defines are used in API file lmb.h and not only in library file.

Fixes: 5e2548c1d6e03 ("lmb: Fix LMB_MEMORY_REGIONS flag usage")
Reported-by: Mark Millard <marklmi@yahoo.com>
Signed-off-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
Acked-by: Michal Simek <michal.simek@amd.com>
diff --git a/lib/Kconfig b/lib/Kconfig
index 202a34a..d8dac09 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -1057,7 +1057,6 @@
 
 config LMB_USE_MAX_REGIONS
 	bool "Use a common number of memory and reserved regions in lmb lib"
-	depends on LMB
 	default y
 	help
 	  Define the number of supported memory regions in the library logical
@@ -1067,7 +1066,7 @@
 
 config LMB_MAX_REGIONS
 	int "Number of memory and reserved regions in lmb lib"
-	depends on LMB && LMB_USE_MAX_REGIONS
+	depends on LMB_USE_MAX_REGIONS
 	default 16
 	help
 	  Define the number of supported regions, memory and reserved, in the
@@ -1075,7 +1074,7 @@
 
 config LMB_MEMORY_REGIONS
 	int "Number of memory regions in lmb lib"
-	depends on LMB && !LMB_USE_MAX_REGIONS
+	depends on !LMB_USE_MAX_REGIONS
 	default 8
 	help
 	  Define the number of supported memory regions in the library logical
@@ -1084,7 +1083,7 @@
 
 config LMB_RESERVED_REGIONS
 	int "Number of reserved regions in lmb lib"
-	depends on LMB && !LMB_USE_MAX_REGIONS
+	depends on !LMB_USE_MAX_REGIONS
 	default 8
 	help
 	  Define the number of supported reserved regions in the library logical