hw/primecell.h: Remove obsolete pl080_init() declaration

Remove an obsolete declaration of pl080_init(), which has been
incorrect since the conversion of pl080 to qdev back in 2009.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

hw/primecell.h

@@ -5,9 +5,6 @@
 /* Also includes some devices that are currently only used by the
    ARM boards.  */
 
-/* pl080.c */
-void *pl080_init(uint32_t base, qemu_irq irq, int nchannels);
-
 /* arm_sysctl GPIO lines */
 #define ARM_SYSCTL_GPIO_MMC_WPROT 0
 #define ARM_SYSCTL_GPIO_MMC_CARDIN 1