misc: stm32_fuse: Fix warnings when compiling with W=1

misc: stm32_fuse: Fix warnings when compiling with W=1

This patch solves the following warnings:

warning: no previous prototype for 'fuse_read' [-Wmissing-prototypes]
 int fuse_read(u32 bank, u32 word, u32 *val)
     ^~~~~~~~~
  CC      cmd/sf.o
warning: no previous prototype for 'fuse_prog' [-Wmissing-prototypes]
 int fuse_prog(u32 bank, u32 word, u32 val)
     ^~~~~~~~~
warning: no previous prototype for 'fuse_sense' [-Wmissing-prototypes]
 int fuse_sense(u32 bank, u32 word, u32 *val)
     ^~~~~~~~~~
warning: no previous prototype for 'fuse_override' [-Wmissing-prototypes]
 int fuse_override(u32 bank, u32 word, u32 val)
     ^~~~~~~~~~~~~

Signed-off-by: Patrice Chotard <patrice.chotard@st.com>
Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>