clocksource: Make the int help prompt unit readable in ncurses

When doing

make menuconfig

and searching for the CLOCKSOURCE_WATCHDOG_MAX_SKEW_US config item, the
help says:

│ Symbol: CLOCKSOURCE_WATCHDOG_MAX_SKEW_US [=125]
│ Type : integer
│ Range : [50 1000]
│ Defined at kernel/time/Kconfig:204
│ Prompt: Clocksource watchdog maximum allowable skew (in s)
^^^

│ Depends on: GENERIC_CLOCKEVENTS [=y] && CLOCKSOURCE_WATCHDOG [=y]

because on some terminals, it cannot display the 'μ' char, unicode
number 0x3bc.

So simply write it out so that there's no trouble.

Signed-off-by: Borislav Petkov (AMD) <[e-mail]>
Signed-off-by: Thomas Gleixner <[e-mail]>
Acked-by: Paul E. McKenney <[e-mail]>
Acked-by: Randy Dunlap <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

kernel/time/Kconfig

···
 	  the size of the kernel image.
 
 config CLOCKSOURCE_WATCHDOG_MAX_SKEW_US
-	int "Clocksource watchdog maximum allowable skew (in μs)"
+	int "Clocksource watchdog maximum allowable skew (in microseconds)"
 	depends on CLOCKSOURCE_WATCHDOG
 	range 50 1000
 	default 125