[initrd] Rename bzimage_align() to initrd_align()

Alignment of initrd lengths is applicable to all Linux kernels, not
just those in the x86 bzImage format.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/include/ipxe/cpio.h

@@ -60,9 +60,6 @@ struct cpio_header {
 /** CPIO header length alignment */
 #define CPIO_ALIGN 4
 
-/** Alignment for CPIO archives within an initrd */
-#define INITRD_ALIGN 4096
-
 /**
  * Get CPIO image name
  *

src/include/ipxe/initrd.h

@@ -14,4 +14,19 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 extern void initrd_reshuffle ( physaddr_t bottom );
 extern int initrd_reshuffle_check ( size_t len, physaddr_t bottom );
 
+/** Initial ramdisk chunk alignment */
+#define INITRD_ALIGN 4096
+
+/**
+ * Align initrd length
+ *
+ * @v len		Length
+ * @ret len		Aligned length
+ */
+static inline __attribute__ (( always_inline )) size_t
+initrd_align ( size_t len ) {
+
+	return ( ( len + INITRD_ALIGN - 1 ) & ~( INITRD_ALIGN - 1 ) );
+}
+
 #endif /* _IPXE_INITRD_H */