[ARM] 2941/1: Fix running legacy binaries from a soft-float root filesystem with CONFIG_IWMMXT.

Patch from Daniel Jacobowitz

Thread flags are inherited on fork().  In order for a binary which has
the iWMMXt coprocessor enabled to run a binary which needs the FPA
emulation, we need to explicitly clear TIF_USING_IWMMXT if we are not
going to set it.
Signed-off-by: NDaniel Jacobowitz <dan@codesourcery.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

include/asm-arm/elf.h

@@ -124,6 +124,8 @@ do { \
 	if (((ex).e_flags & EF_ARM_EABI_MASK) || \
 	    ((ex).e_flags & EF_ARM_SOFT_FLOAT)) \
 		set_thread_flag(TIF_USING_IWMMXT); \
+	else \
+		clear_thread_flag(TIF_USING_IWMMXT); \
 } while (0)
 
 #endif