xpl: Rename u_boot_first_phase to xpl_is_first_phase()

This is a better name for this function, so update it.

Tidy up the function comment to mention VPL.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/include/spl.h b/include/spl.h
index de808cc..fa87d86 100644
--- a/include/spl.h
+++ b/include/spl.h
@@ -34,18 +34,20 @@
 enum boot_device;
 
 /*
- * u_boot_first_phase() - check if this is the first U-Boot phase
+ * xpl_is_first_phase() - check if this is the first U-Boot phase
  *
- * U-Boot has up to three phases: TPL, SPL and U-Boot proper. Depending on the
- * build flags we can determine whether the current build is for the first
+ * U-Boot has up to four phases: TPL, VPL, SPL and U-Boot proper. Depending on
+ * the build flags we can determine whether the current build is for the first
  * phase of U-Boot or not. If there is no SPL, then this is U-Boot proper. If
  * there is SPL but no TPL, the the first phase is SPL. If there is TPL, then
- * it is the first phase.
+ * it is the first phase, etc.
  *
- * @returns true if this is the first phase of U-Boot
+ * Note that VPL can never be the first phase. If it exists, it is loaded from
+ * TPL
  *
+ * Return: true if this is the first phase of U-Boot
  */
-static inline bool u_boot_first_phase(void)
+static inline bool xpl_is_first_phase(void)
 {
 	if (IS_ENABLED(CONFIG_TPL)) {
 		if (IS_ENABLED(CONFIG_TPL_BUILD))