irqchip/irq-pruss-intc: Fix incorrect macro replacement
The commit 57c76b3f2804 ("irqchip/irq-pruss-intc: Use macros
for operations on CMR and HMR") mistakenly replaced the number
of channels per Host Interrupt Map Register (4) with the wrong
macro HMR_CH_MAP_BITS which is the number of shift-bits to be
used per channel. Use the correct macro to fix this typo.
Fixes: 57c76b3f2804 ("irqchip/irq-pruss-intc: Use macros for operations on CMR and HMR")
Signed-off-by: Suman Anna <s-anna@ti.com>