arm: msm: trout: fix compile failure

Fixes the following warnings,

arch/arm/mach-msm/board-trout.c: In function 'trout_init':
arch/arm/mach-msm/board-trout.c:71: error: 'system_rev' undeclared (first use in this function)
arch/arm/mach-msm/board-trout.c:71: error: (Each undeclared identifier is reported only once
arch/arm/mach-msm/board-trout.c:71: error: for each function it appears in.)

and

arch/arm/mach-msm/board-trout-panel.c: In function 'trout_init_panel':
arch/arm/mach-msm/board-trout-panel.c:267: error: 'system_rev' undeclared (first use in this function)
arch/arm/mach-msm/board-trout-panel.c:267: error: (Each undeclared identifier is reported only once
arch/arm/mach-msm/board-trout-panel.c:267: error: for each function it appears in.)

This came in with the following commit 9f97da78
which removes asm/system.h

Signed-off-by: Daniel Walker <dwalker@fifo99.com>
cc: David Howells <dhowells@redhat.com>
cc: Bryan Huntsman <bryanh@codeaurora.org>
cc: linux-arm-msm@vger.kernel.org
cc: linux-arm-kernel@lists.infradead.org
Signed-off-by: David Brown <davidb@codeaurora.org>