post: remove reference to power functions

The 2 functions board_power_mode and board_poweroff
are no more existing in U-Boot code (check with grep)
This patch updates the documentation and removes
the unnecessary prototypes.

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>

doc/README.POST

@@ -159,17 +159,6 @@ The POST layer will export the following interface routines:
 Also, the following board-specific routines will be called from the
 U-Boot common code:
 
-  o) int board_power_mode(void)
-
-     This routine will return the mode the system is running in
-     (POST_POWERON, POST_NORMAL or POST_SHUTDOWN).
-
-  o) void board_poweroff(void)
-
-     This routine will turn off the power supply of the board. It
-     will be called on power-fail booting after running all POST
-     tests.
-
   o) int post_hotkeys_pressed(gd_t *gd)
 
      This routine will scan the keyboard to detect if a magic key

include/common.h

@@ -415,7 +415,6 @@ int board_fix_fdt (void *rw_fdt_blob); /* manipulate the U-Boot fdt before its r
 int board_late_init (void);
 int board_postclk_init (void); /* after clocks/timebase, before env/serial */
 int board_early_init_r (void);
-void board_poweroff (void);
 
 #if defined(CONFIG_SYS_DRAM_TEST)
 int testdram(void);