Remove confusing const qualifier

Since a is not a pointer, it is passed by value and declaring it const
doesn’t make any sense and on the first read can make me miss the fact
that a is not a pointer.

Signed-off-by: Janos Follath <janos.follath@arm.com>
diff --git a/library/bignum_core.c b/library/bignum_core.c
index 15557e6..8e89766 100644
--- a/library/bignum_core.c
+++ b/library/bignum_core.c
@@ -38,7 +38,7 @@
 
 #include "bignum_core.h"
 
-size_t mbedtls_mpi_core_clz( const mbedtls_mpi_uint a )
+size_t mbedtls_mpi_core_clz( mbedtls_mpi_uint a )
 {
     size_t j;
     mbedtls_mpi_uint mask = (mbedtls_mpi_uint) 1 << (biL - 1);