genirq: Fix typo CONFIG_GENIRC_IRQ_SHOW_LEVEL

genirq: Fix typo CONFIG_GENIRC_IRQ_SHOW_LEVEL

commit ab7798ffcf98b11a9525cf65bacdae3fd58d357f ("genirq: Expand generic
show_interrupts()") added the Kconfig option GENERIC_IRQ_SHOW_LEVEL to
accomodate PowerPC, but this doesn't actually enable the functionality due
to a typo in the #ifdef check.

Signed-off-by: Geert Uytterhoeven <[email protected]>
Cc: Linux/PPC Development <[email protected]>
Link: http://lkml.kernel.org/r/%3Calpine.DEB.2.00.1104302251370.19068%40ayla.of.borg%3E
Signed-off-by: Thomas Gleixner <[email protected]>