firmware: arm_ffa: Align RxTx buffer size before mapping

Commit 8321025 ("firmware: arm_ffa: Use the correct buffer size during
RXTX_MAP") advertises PAGE_ALIGN(rxtx_bufsz) to firmware when mapping the
buffers but the driver continues to stores the minimum FF-A buffer size
in drv_info->rxtx_bufsz which is used elsewhere in the driver.

Align the size before storing it so that the allocation, validation and
FFA_RXTX_MAP all use the same buffer size.

Fixes: 8321025 ("firmware: arm_ffa: Use the correct buffer size during RXTX_MAP")
Cc: Sebastian Ene <sebastianene@google.com>
Link: https://sashiko.dev/#/patchset/20260402113939.930221-1-sebastianene@google.com
Reviewed-by: Sebastian Ene <sebastianene@google.com>
Link: https://patch.msgid.link/20260428-ffa_fixes-v2-9-8595ae450034@kernel.org
Signed-off-by: Sudeep Holla <sudeep.holla@kernel.org>

Author: Sudeep Holla

drivers/firmware/arm_ffa/driver.c

@@ -2109,6 +2109,7 @@ static int __init ffa_init(void)
 			rxtx_bufsz = SZ_4K;
 	}
 
+	rxtx_bufsz = PAGE_ALIGN(rxtx_bufsz);
 	drv_info->rxtx_bufsz = rxtx_bufsz;
 	drv_info->rx_buffer = alloc_pages_exact(rxtx_bufsz, GFP_KERNEL);
 	if (!drv_info->rx_buffer) {
@@ -2124,7 +2125,7 @@ static int __init ffa_init(void)
 
 	ret = ffa_rxtx_map(virt_to_phys(drv_info->tx_buffer),
 			   virt_to_phys(drv_info->rx_buffer),
-			   PAGE_ALIGN(rxtx_bufsz) / FFA_PAGE_SIZE);
+			   rxtx_bufsz / FFA_PAGE_SIZE);
 	if (ret) {
 		pr_err("failed to register FFA RxTx buffers\n");
 		goto free_pages;