ARM: omap1: remove unused variable

The cleanup of the debugfs functions left one variable behind that
should now be removed as well:

arch/arm/mach-omap1/clock.c:1008:6: error: unused variable 'err' [-Werror,-Wunused-variable]

Fixes: d5ddd5a5 ("arm: omap1: no need to check return value of debugfs_create functions")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>