Change bits to digits in comment

The string holds hex digits each representing 4 bits for total space for
64 bits on the prior line.

Change-Id: I31be090682d96c6c4cb178b99d7c0f43f8afafc4
Signed-off-by: Milton Miller <mdmii@outlook.com>
diff --git a/include/libcper/Cper.h b/include/libcper/Cper.h
index 91776d0..48038e1 100644
--- a/include/libcper/Cper.h
+++ b/include/libcper/Cper.h
@@ -53,7 +53,7 @@
 
 ///
 /// Hexadecimal string representation of a 64bit integer
-/// 16 bits + 2 char + 1 null termination
+/// 16 digits + 2 char + 1 null termination
 ///
 #define EFI_UINT64_HEX_STRING_LEN 19