ARM: davinci: fix sleep.S build error on ARMv4

When building a multiplatform kernel that includes armv4 support,
the default target CPU does not support the blx instruction,
which leads to a build failure:

arch/arm/mach-davinci/sleep.S: Assembler messages:
arch/arm/mach-davinci/sleep.S:56: Error: selected processor does not support `blx ip' in ARM mode

Add a .arch statement in the sources to make this file build.

Link: https://lore.kernel.org/r/20190722145211.1154785-1-arnd@arndb.deAcked-by: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Olof Johansson <olof@lixom.net>

arch/arm/mach-davinci/sleep.S

@@ -24,6 +24,7 @@
 #define DEEPSLEEP_SLEEPENABLE_BIT	BIT(31)
 
 	.text
+	.arch	armv5te
 /*
  * Move DaVinci into deep sleep state
  *