omap3: Drop CONFIG_OMAP3_EVM, switch to CONFIG_TARGET_OMAP3_EVM when needed

We make use of CONFIG_OMAP3_EVM today to know when to do a specific
tweak in MUSB.  This can be tested on via CONFIG_TARGET_OMAP3_EVM
instead, so switch there so we can drop the now unused symbol
CONFIG_OMAP3_EVM.  In investigating what to do about the symbol usage we
see that the cairo board defines the same function, but never called it
(as it does not define CONFIG_OMAP3_EVM) and was just returning anyhow,
so drop that function from that board.

Cc: "Albert ARIBAUD (3ADEV)" <albert.aribaud@3adev.fr>
Cc: Marek Vasut <marex@denx.de>
Signed-off-by: Tom Rini <trini@konsulko.com>

board/quipos/cairo/cairo.c

@@ -25,18 +25,6 @@
 
 DECLARE_GLOBAL_DATA_PTR;
 
-/*
- * MUSB port on OMAP3EVM Rev >= E requires extvbus programming.
- */
-u8 omap3_evm_need_extvbus(void)
-{
-	u8 retval = 0;
-
-	/* TODO: verify if cairo handheld platform needs extvbus programming */
-
-	return retval;
-}
-
 /*
  * Routine: board_init
  * Description: Early hardware init.