ARM: OMAP1: clock: Fix UART rate reporting algorithm

Since its introduction to the mainline kernel, omap1_uart_recalc() helper
makes incorrect use of clk->enable_bit as a ready to use bitmap mask while
it only provides the bit number.  Fix it.

Signed-off-by: Janusz Krzysztofik <jmkrzyszt@gmail.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>